func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    var i = 0
    while i < numbers.count - 1 {
        let diff = numbers[i + 1] - numbers[i]
        if diff < threshold {
            return true
        }
        i += 1
    }
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    var i = 0
    while i < numbers.count - 1 {
        let diff = numbers[i + 1] - numbers[i]
        if diff < threshold {
            return true
        }
        i += 1
    }
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: implement
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: implement
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    guard numbers.count > 1 else { return false }
    for i in 0..<numbers.count - 1 {
        for j in i + 1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    guard numbers.count > 1 else { return false }
    for i in 0..<numbers.count - 1 {
        for j in i + 1..<numbers.count {
            if abs(numbers[i] - numbers[j]) < threshold {
                return true
            }
        }
    }
    return false
}
```

func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}

```swift
// Check if in given array of numbers, are any two numbers closer to each other than
// given threshold.
// hasCloseElements(numbers: [1.0, 2.0, 3.0], threshold: 0.5) == false
// hasCloseElements(numbers: [1.0, 2.8, 3.0, 4.0, 5.0, 2.0], threshold: 0.3) == true
func hasCloseElements(numbers: [Double], threshold: Double) -> Bool {
    // TODO: Implement this function.
    return false
}
```

func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}
```

func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}
```

func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
}
```

func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}
```

func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}
```

func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // Your code here
}
```

func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}
```

func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}
```

func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}
```

func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string containing multiple groups of nested parentheses. Your goal is to
// separate those group into separate strings and return the array of those.
// Separate groups are balanced (each open brace is properly closed) and not nested within each other
// Ignore any spaces in the input string.
// separateParenGroups(parenString: "( ) (( )) (( )( ))") == ["()", "(())", "(()())"]
func separateParenGroups(parenString: String) -> [String] {
    // TODO: Implement this function
    return []
}
```

func truncateNumber(number: Double) -> Double {
    // Your code here
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // Your code here
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Your code here
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Your code here
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}
```

func truncateNumber(number: Double) -> Double {
    // Your code here
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // Your code here
}
```

func truncateNumber(number: Double) -> Double {
    // Your code here
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // Your code here
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}
```

func truncateNumber(number: Double) -> Double {
    return number.truncatingRemainder(dividingBy: 1)
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    return number.truncatingRemainder(dividingBy: 1)
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Write your code here
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Write your code here
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
}
```

func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
    return 0
}

```swift
// Given a positive floating point number, it can be decomposed into
// and integer part (largest integer smaller than given number) and decimals
// (leftover part always smaller than 1).
// Return the decimal part of the number.
// truncateNumber(number: 3.5) == 0.5
func truncateNumber(number: Double) -> Double {
    // TODO: Implement this function
    return 0
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}

```swift
// You're given an array of deposit and withdrawal operations on a bank account that starts with
// zero balance. Your task is to detect if at any point the balance of account fallls below zero, and
// at that point function should return true. Otherwise it should return false.
// belowZero(operations: [1, 2, 3]) == false
// belowZero(operations: [1, 2, -4, 5]) == true
func belowZero(operations: [Int]) -> Bool {
    var balance = 0
    for operation in operations {
        balance += operation
        if balance < 0 {
            return true
        }
    }
    return false
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    let absoluteDeviations = numbers.map { abs($0 - mean) }
    return absoluteDeviations.mean()
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    let absoluteDeviations = numbers.map { abs($0 - mean) }
    return absoluteDeviations.mean()
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    let differences = numbers.map { abs($0 - mean) }
    return differences.mean()
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    let differences = numbers.map { abs($0 - mean) }
    return differences.mean()
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(deviations.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(deviations.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    return numbers.map { abs($0 - mean) }.mean()
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.mean()
    return numbers.map { abs($0 - mean) }.mean()
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0.0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0.0, +) / Double(numbers.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0.0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0.0, +) / Double(numbers.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(deviations.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(deviations.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    return numbers.map { abs($0 - mean) }.reduce(0, +) / Double(numbers.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    return numbers.map { abs($0 - mean) }.reduce(0, +) / Double(numbers.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(numbers.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let deviations = numbers.map { abs($0 - mean) }
    return deviations.reduce(0, +) / Double(numbers.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let differences = numbers.map { abs($0 - mean) }
    return differences.reduce(0, +) / Double(numbers.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let differences = numbers.map { abs($0 - mean) }
    return differences.reduce(0, +) / Double(numbers.count)
}
```

func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let absDeviations = numbers.map { abs($0 - mean) }
    return absDeviations.reduce(0, +) / Double(absDeviations.count)
}

```swift
// For a given array of input numbers, calculate Mean Absolute Deviation
// around the mean of this dataset.
// Mean Absolute Deviation is the average absolute difference between each
// element and a centerpoint (mean in this case):
// MAD = average | x - x_mean |
// meanAbsoluteDeviation(numbers: [1.0, 2.0, 3.0, 4.0]) == 1.0
func meanAbsoluteDeviation(numbers: [Double]) -> Double {
    let mean = numbers.reduce(0, +) / Double(numbers.count)
    let absDeviations = numbers.map { abs($0 - mean) }
    return absDeviations.reduce(0, +) / Double(absDeviations.count)
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 1 else { return numbers }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 1 else { return numbers }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    var result = [Int]()
    for (index, number) in numbers.enumerate() {
        result.append(number)
        if index!= numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    return numbers.reduce([]) { (result, number) -> [Int] in
        return result + [number, delimeter]
    }.dropLast()
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    return numbers.reduce([]) { (result, number) -> [Int] in
        return result + [number, delimeter]
    }.dropLast()
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    return numbers.reduce([]) { (result, number) in
        return result + [number, delimeter]
    }
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    return numbers.reduce([]) { (result, number) in
        return result + [number, delimeter]
    }
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index < numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index < numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index < numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    guard numbers.count > 0 else { return [] }
    var result = [Int]()
    for (index, number) in numbers.enumerated() {
        result.append(number)
        if index < numbers.count - 1 {
            result.append(delimeter)
        }
    }
    return result
}
```

func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Insert a number 'delimeter' between every two consecutive elements of input array `numbers'
// intersperse(numbers: [] as [Int], delimeter: 4) == [] as [Int]
// intersperse(numbers: [1, 2, 3], delimeter: 4) == [1, 4, 2, 4, 3]
func intersperse(numbers: [Int], delimeter: Int) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Write your code here.
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Write your code here.
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function.
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function.
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function.
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function.
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func parseNestedParens(parenString: String) -> [Int] {
    var result = [Int]()
    let parenGroups = parenString.components(separatedBy: " ")
    for parenGroup in parenGroups {
        result.append(parseNestedParens(parenGroup: parenGroup))
    }
    return result
}

func parseNestedParens(parenGroup: String) -> Int {
    var maxDepth = 0
    var currentDepth = 0
    for char in parenGroup {
        if char == "(" {
            currentDepth += 1
            maxDepth = max(maxDepth, currentDepth)
        } else if char == ")" {
            currentDepth -= 1
        }
    }
    return maxDepth
}

```swift
// Input to this function is a string represented multiple groups for nested parentheses separated by spaces.
// For each of the group, output the deepest level of nesting of parentheses.
// E.g. (()()) has maximum two levels of nesting while ((())) has three.
// parseNestedParens(parenString: "(()()) ((())) () ((())()())") == [2, 3, 1, 3]
func parseNestedParens(parenString: String) -> [Int] {
    var result = [Int]()
    let parenGroups = parenString.components(separatedBy: " ")
    for parenGroup in parenGroups {
        result.append(parseNestedParens(parenGroup: parenGroup))
    }
    return result
}

// Helper function to parse a single group of nested parentheses.
func parseNestedParens(parenGroup: String) -> Int {
    var maxDepth = 0
    var currentDepth = 0
    for char in parenGroup {
        if char == "(" {
            currentDepth += 1
            maxDepth = max(maxDepth, currentDepth)
        } else if char == ")" {
            currentDepth -= 1
        }
    }
    return maxDepth
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}

```swift
// Filter an input array of strings only for ones that contain given substring
// filterBySubstring(strings: [] as [String], substring: "a") == [] as [String]
// filterBySubstring(strings: ["abc", "bacd", "cde", "array"], substring: "a") == ["abc", "bacd", "array"]
func filterBySubstring(strings: [String], substring: String) -> [String] {
    return strings.filter { $0.contains(substring) }
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}

```swift
// For a given array of integers, return a tuple consisting of a sum and a product of all the integers in an array.
// Empty sum should be equal to 0 and empty product should be equal to 1.
// sumProduct(numbers: [] as [Int]) == (0, 1)
// sumProduct(numbers: [1, 2, 3, 4]) == (10, 24)
func sumProduct(numbers: [Int]) -> (Int, Int) {
    var sum = 0
    var product = 1
    for number in numbers {
        sum += number
        product *= number
    }
    return (sum, product)
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var max = numbers[0]
    var result = [Int]()
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var max = numbers[0]
    var result = [Int]()
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = 0
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = 0
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = Int.min
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = Int.min
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}

```swift
// From a given array of integers, generate an array of rolling maximum element found until given moment
// in the sequence.
// rollingMax(numbers: [1, 2, 3, 2, 3, 4, 2]) == [1, 2, 3, 3, 3, 4, 4]
func rollingMax(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var max = numbers[0]
    for number in numbers {
        if number > max {
            max = number
        }
        result.append(max)
    }
    return result
}
```

func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!postfix.isEmpty {
        if reversedString.hasPrefix(postfix) {
            return string + String(prefix.reversed())
        }
        prefix.append(postfix.removeLast())
    }
    return string + String(prefix.reversed())
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!postfix.isEmpty {
        if reversedString.hasPrefix(postfix) {
            return string + String(prefix.reversed())
        }
        prefix.append(postfix.removeLast())
    }
    return string + String(prefix.reversed())
}
```

func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    let reversedPrefix = reversedString.prefix(string.count - longestPalindromicSuffix(string: string))
    return string + String(reversedPrefix)
}

func longestPalindromicSuffix(string: String) -> String {
    let reversedString = String(string.reversed())
    let reversedPrefix = reversedString.prefix(string.count)
    let reversedSuffix = reversedString.suffix(string.count)
    let reversedPrefixArray = Array(reversedPrefix)
    let reversedSuffixArray = Array(reversedSuffix)
    var longestPalindromicSuffix = ""
    for i in 0..<reversedPrefixArray.count {
        if reversedPrefixArray[i] == reversedSuffixArray[i] {
            longestPalindromicSuffix.append(reversedPrefixArray[i])
        } else {
            break
        }
    }
    return String(longestPalindromicSuffix.reversed())
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    let reversedPrefix = reversedString.prefix(string.count - longestPalindromicSuffix(string: string))
    return string + String(reversedPrefix)
}

// Finds the longest palindromic suffix of a string.
// longestPalindromicSuffix(string: "") == ""
// longestPalindromicSuffix(string: "cat") == ""
// longestPalindromicSuffix(string: "cata") == "a"
// longestPalindromicSuffix(string: "catac") == "catac"
func longestPalindromicSuffix(string: String) -> String {
    let reversedString = String(string.reversed())
    let reversedPrefix = reversedString.prefix(string.count)
    let reversedSuffix = reversedString.suffix(string.count)
    let reversedPrefixArray = Array(reversedPrefix)
    let reversedSuffixArray = Array(reversedSuffix)
    var longestPalindromicSuffix = ""
    for i in 0..<reversedPrefixArray.count {
        if reversedPrefixArray[i] == reversedSuffixArray[i] {
            longestPalindromicSuffix.append(reversedPrefixArray[i])
        } else {
            break
        }
    }
    return String(longestPalindromicSuffix.reversed())
}
```

func makePalindrome(string: String) -> String {
    if string.isEmpty {
        return string
    }
    let reversed = String(string.reversed())
    var prefix = ""
    var suffix = string
    while!suffix.isEmpty {
        if prefix + suffix == reversed {
            return string + String(reversed.dropFirst(prefix.count))
        }
        prefix.append(suffix.removeFirst())
    }
    return string + String(reversed.reversed())
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    if string.isEmpty {
        return string
    }
    let reversed = String(string.reversed())
    var prefix = ""
    var suffix = string
    while!suffix.isEmpty {
        if prefix + suffix == reversed {
            return string + String(reversed.dropFirst(prefix.count))
        }
        prefix.append(suffix.removeFirst())
    }
    return string + String(reversed.reversed())
}
```

func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!postfix.isEmpty {
        if reversedString.hasPrefix(postfix) {
            return string + String(prefix.reversed())
        }
        prefix.append(postfix.removeLast())
    }
    return string + String(prefix.reversed())
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!postfix.isEmpty {
        if reversedString.hasPrefix(postfix) {
            return string + String(prefix.reversed())
        }
        prefix.append(postfix.removeLast())
    }
    return string + String(prefix.reversed())
}
```

func makePalindrome(string: String) -> String {
    if string.isEmpty {
        return ""
    }
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!prefix.isEmpty ||!postfix.isEmpty {
        if prefix == reversedString {
            return string + String(postfix.reversed())
        }
        prefix.append(postfix.removeFirst())
        postfix.append(prefix.removeLast())
    }
    return string
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    if string.isEmpty {
        return ""
    }
    let reversedString = String(string.reversed())
    var prefix = ""
    var postfix = string
    while!prefix.isEmpty ||!postfix.isEmpty {
        if prefix == reversedString {
            return string + String(postfix.reversed())
        }
        prefix.append(postfix.removeFirst())
        postfix.append(prefix.removeLast())
    }
    return string
}
```

func makePalindrome(string: String) -> String {
    guard!string.isEmpty else { return "" }
    let reversed = string.reversed()
    var prefix = ""
    var postfix = ""
    var i = 0
    while i < string.count {
        if string[string.index(string.startIndex, offsetBy: i)] == reversed[reversed.index(reversed.startIndex, offsetBy: i)] {
            prefix.append(string[string.index(string.startIndex, offsetBy: i)])
            postfix.append(reversed[reversed.index(reversed.startIndex, offsetBy: i)])
        } else {
            break
        }
        i += 1
    }
    return string + postfix.reversed()
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    guard!string.isEmpty else { return "" }
    let reversed = string.reversed()
    var prefix = ""
    var postfix = ""
    var i = 0
    while i < string.count {
        if string[string.index(string.startIndex, offsetBy: i)] == reversed[reversed.index(reversed.startIndex, offsetBy: i)] {
            prefix.append(string[string.index(string.startIndex, offsetBy: i)])
            postfix.append(reversed[reversed.index(reversed.startIndex, offsetBy: i)])
        } else {
            break
        }
        i += 1
    }
    return string + postfix.reversed()
}
```

func makePalindrome(string: String) -> String {
    guard string.count > 1 else { return string }
    let reversed = String(string.reversed())
    var prefix = ""
    var suffix = string
    while suffix.count > 0 {
        if reversed.hasPrefix(suffix) {
            return string + prefix
        }
        prefix.append(suffix.removeLast())
    }
    return string
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    guard string.count > 1 else { return string }
    let reversed = String(string.reversed())
    var prefix = ""
    var suffix = string
    while suffix.count > 0 {
        if reversed.hasPrefix(suffix) {
            return string + prefix
        }
        prefix.append(suffix.removeLast())
    }
    return string
}
```

func makePalindrome(string: String) -> String {
    let reversed = String(string.characters.reversed())
    let prefix = string.substring(to: string.index(string.startIndex, offsetBy: longestPalindromePrefix(string: string)))
    return string + reversed.substring(from: reversed.index(reversed.startIndex, offsetBy: prefix.characters.count))
}

func longestPalindromePrefix(string: String) -> Int {
    var longestPrefix = 0
    var currentPrefix = 0
    var currentSuffix = 0
    let characters = Array(string.characters)
    while currentSuffix < characters.count {
        if currentPrefix == 0 {
            currentSuffix += 1
            currentPrefix = 1
        } else if characters[currentPrefix - 1] == characters[currentSuffix] {
            currentPrefix += 1
            currentSuffix += 1
        } else {
            currentPrefix = 0
        }
        if currentPrefix > longestPrefix {
            longestPrefix = currentPrefix
        }
    }
    return longestPrefix
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversed = String(string.characters.reversed())
    let prefix = string.substring(to: string.index(string.startIndex, offsetBy: longestPalindromePrefix(string: string)))
    return string + reversed.substring(from: reversed.index(reversed.startIndex, offsetBy: prefix.characters.count))
}

// Find the longest palindrome prefix of a string.
// longestPalindromePrefix(string: "") == 0
// longestPalindromePrefix(string: "cat") == 0
// longestPalindromePrefix(string: "cata") == 1
// longestPalindromePrefix(string: "catac") == 4
// longestPalindromePrefix(string: "cataca") == 4
// longestPalindromePrefix(string: "catacab") == 4
func longestPalindromePrefix(string: String) -> Int {
    var longestPrefix = 0
    var currentPrefix = 0
    var currentSuffix = 0
    let characters = Array(string.characters)
    while currentSuffix < characters.count {
        if currentPrefix == 0 {
            currentSuffix += 1
            currentPrefix = 1
        } else if characters[currentPrefix - 1] == characters[currentSuffix] {
            currentPrefix += 1
            currentSuffix += 1
        } else {
            currentPrefix = 0
        }
        if currentPrefix > longestPrefix {
            longestPrefix = currentPrefix
        }
    }
    return longestPrefix
}
```

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversedString = String(string.reversed())
    let reversedPrefix = reversedString.prefix(string.count - 1)
    let reversedPrefixString = String(reversedPrefix)
    let reversedPrefixStringWithSeparator = reversedPrefixString + " "
    let reversedPrefixStringWithSeparatorArray = Array(reversedPrefixStringWithSeparator)
    let reversedPrefixStringWithSeparatorArrayReversed = reversedPrefixStringWithSeparatorArray.reversed()
    let reversedPrefixStringWithSeparatorReversed = String(reversedPrefixStringWithSeparatorArrayReversed)
    let reversedPrefixStringWithSeparatorReversedArray = Array(reversedPrefixStringWithSeparatorReversed)
    let reversedPrefixStringWithSeparatorReversedArrayWithoutSpace = reversedPrefixStringWithSeparatorReversedArray.dropLast()
    let reversedPrefixStringWithSeparatorReversedWithoutSpace = String(reversedPrefixStringWithSeparatorReversedArrayWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceArrayReversed = reversedPrefixStringWithSeparatorReversedWithoutSpaceArray.reversed()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversed = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceArrayReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedArrayWithoutSpace = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedArray.dropLast()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpace = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedArrayWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceArrayReversed = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceArray.reversed()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversed = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceArrayReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedArrayWithoutSpace = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedArray.dropLast()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpace = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedArrayWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArrayReversed = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArray.reversed()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversed = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArrayReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedArrayWithoutSpace = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedArray.dropLast()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpace = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedArrayWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArray = Array(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpace)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArrayReversed = reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArray.reversed()
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversed = String(reversedPrefixStringWithSeparatorReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceReversedWithoutSpaceArrayReversed)
    let reversedPrefixStringWithSeparatorReversedWithoutSpaceReversed

func makePalindrome(string: String) -> String {
    let reversed = string.reversed()
    let reversedPrefix = reversed.prefix(while: {!string.contains($0) })
    return string + String(reversedPrefix)
}

```swift
// Find the shortest palindrome that begins with a supplied string.
// Algorithm idea is simple:
// - Find the longest postfix of supplied string that is a palindrome.
// - Append to the end of the string reverse of a string prefix that comes before the palindromic suffix.
// makePalindrome(string: "") == ""
// makePalindrome(string: "cat") == "catac"
// makePalindrome(string: "cata") == "catac"
func makePalindrome(string: String) -> String {
    let reversed = string.reversed()
    let reversedPrefix = reversed.prefix(while: {!string.contains($0) })
    return string + String(reversedPrefix)
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        if char == b[b.startIndex.advancedBy(index)] {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        if char == b[b.startIndex.advancedBy(index)] {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func stringXor(a: String, b: String) -> String {
    // your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // your code here
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        let bChar = b.characters[b.characters.index(b.startIndex, offsetBy: index)]
        if char == bChar {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        let bChar = b.characters[b.characters.index(b.startIndex, offsetBy: index)]
        if char == bChar {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}
```

func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        if char == b.characters[b.startIndex.advancedBy(index)] {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    var result = ""
    for (index, char) in a.characters.enumerate() {
        if char == b.characters[b.startIndex.advancedBy(index)] {
            result += "0"
        } else {
            result += "1"
        }
    }
    return result
}
```

func stringXor(a: String, b: String) -> String {
    // Your code here
}

```swift
// Input are two strings a and b consisting only of 1s and 0s.
// Perform binary XOR on these inputs and return result also as a string.
// stringXor(a: "010", b: "110") == "100"
func stringXor(a: String, b: String) -> String {
    // Your code here
}
```

func longest(strings: [String]) -> String? {
    guard!strings.isEmpty else { return nil }
    var longestString = strings[0]
    for string in strings {
        if string.count > longestString.count {
            longestString = string
        }
    }
    return longestString
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    guard!strings.isEmpty else { return nil }
    var longestString = strings[0]
    for string in strings {
        if string.count > longestString.count {
            longestString = string
        }
    }
    return longestString
}
```

func longest(strings: [String]) -> String? {
    return strings.max { $0.count < $1.count }
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max { $0.count < $1.count }
}
```

func longest(strings: [String]) -> String? {
    guard!strings.isEmpty else { return nil }
    var longest = strings[0]
    for string in strings {
        if string.count > longest.count {
            longest = string
        }
    }
    return longest
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    guard!strings.isEmpty else { return nil }
    var longest = strings[0]
    for string in strings {
        if string.count > longest.count {
            longest = string
        }
    }
    return longest
}
```

func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}
```

func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}
```

func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}
```

func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}
```

func longest(strings: [String]) -> String? {
    guard strings.count > 0 else {
        return nil
    }
    var longestString = strings[0]
    for string in strings {
        if string.count > longestString.count {
            longestString = string
        }
    }
    return longestString
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    guard strings.count > 0 else {
        return nil
    }
    var longestString = strings[0]
    for string in strings {
        if string.count > longestString.count {
            longestString = string
        }
    }
    return longestString
}
```

func longest(strings: [String]) -> String? {
    return strings.max { $0.count < $1.count }
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max { $0.count < $1.count }
}
```

func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}

```swift
// Out of array of strings, return the longest one. Return the first one in case of multiple
// strings of the same length. Return nil in case the input array is empty.
// longest(strings: [] as [String]) == nil
// longest(strings: ["a", "b", "c"]) == "a"
// longest(strings: ["a", "bb", "ccc"]) == "ccc"
func longest(strings: [String]) -> String? {
    return strings.max(by: { $0.count < $1.count })
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    let min = a < b? a : b
    let max = a > b? a : b
    var gcd = 1
    for i in 1...min {
        if a % i == 0 && b % i == 0 {
            gcd = i
        }
    }
    return gcd
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    let min = a < b? a : b
    let max = a > b? a : b
    var gcd = 1
    for i in 1...min {
        if a % i == 0 && b % i == 0 {
            gcd = i
        }
    }
    return gcd
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    // TODO: Write your code here
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    // TODO: Write your code here
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    return 0
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    return 0
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}

```swift
// Return a greatest common divisor of two integers a and b
// greatestCommonDivisor(a: 3, b: 5) == 1
// greatestCommonDivisor(a: 25, b: 15) == 5
func greatestCommonDivisor(a: Int, b: Int) -> Int {
    if b == 0 {
        return a
    } else {
        return greatestCommonDivisor(a: b, b: a % b)
    }
}
```

func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    // TODO: Write your code here
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    // TODO: Write your code here
}
```

func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result: [String] = []
    for i in 0..<string.count {
        result.append(String(string.prefix(i + 1)))
    }
    return result
}
```

func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}

```swift
// Return array of all prefixes from shortest to longest of the input string
// allPrefixes(string: "abc") == ["a", "ab", "abc"]
func allPrefixes(string: String) -> [String] {
    var result = [String]()
    for i in 0..<string.count {
        let index = string.index(string.startIndex, offsetBy: i)
        result.append(String(string[..<index]))
    }
    return result
}
```

func stringSequence(n: Int) -> String {
    // your code here
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    // your code here
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func stringSequence(n: Int) -> String {
    var result = ""
    for i in 0...n {
        result += "\(i) "
    }
    return result.trimmingCharacters(in:.whitespaces)
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    var result = ""
    for i in 0...n {
        result += "\(i) "
    }
    return result.trimmingCharacters(in:.whitespaces)
}
```

func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}

```swift
// Return a string containing space-delimited numbers starting from 0 upto n inclusive.
// stringSequence(n: 0) == "0"
// stringSequence(n: 5) == "0 1 2 3 4 5"
func stringSequence(n: Int) -> String {
    return (0...n).map { String($0) }.joined(separator: " ")
}
```

func countDistinctCharacters(string: String) -> Int {
    // Your code here
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // Your code here
}
```

func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
}
```

func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
}
```

func countDistinctCharacters(string: String) -> Int {
    var count = 0
    var set = Set<Character>()
    for char in string {
        if!set.contains(char) {
            set.insert(char)
            count += 1
        }
    }
    return count
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    var count = 0
    var set = Set<Character>()
    for char in string {
        if!set.contains(char) {
            set.insert(char)
            count += 1
        }
    }
    return count
}
```

func countDistinctCharacters(string: String) -> Int {
    // Your code here
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // Your code here
}
```

func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}
```

func countDistinctCharacters(string: String) -> Int {
    var set = Set<Character>()
    for char in string {
        set.insert(char)
    }
    return set.count
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    var set = Set<Character>()
    for char in string {
        set.insert(char)
    }
    return set.count
}
```

func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}
```

func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    // TODO: Implement this function
    return 0
}
```

func countDistinctCharacters(string: String) -> Int {
    var set = Set<Character>()
    for char in string {
        set.insert(char)
    }
    return set.count
}

```swift
// Given a string, find out how many distinct characters (regardless of case) does it consist of
// countDistinctCharacters(string: "xyzXYZ") == 3
// countDistinctCharacters(string: "Jerry") == 4
func countDistinctCharacters(string: String) -> Int {
    var set = Set<Character>()
    for char in string {
        set.insert(char)
    }
    return set.count
}
```

func parseMusic(musicString: String) -> [Int] {
    // your code here
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    // your code here
}
```

func parseMusic(musicString: String) -> [Int] {
    // Your code here
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    // Your code here
}
```

func parseMusic(musicString: String) -> [Int] {
    // your code here
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    // your code here
}
```

func parseMusic(musicString: String) -> [Int] {
    return []
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    return []
}
```

func parseMusic(musicString: String) -> [Int] {
    // your code here
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    // your code here
}
```

func parseMusic(musicString: String) -> [Int] {
    let notes = musicString.components(separatedBy: " ")
    var result = [Int]()
    for note in notes {
        if note == "o|" {
            result.append(2)
        } else if note == "o" {
            result.append(4)
        } else if note == ".|" {
            result.append(1)
        } else {
            result.append(1)
        }
    }
    return result
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    let notes = musicString.components(separatedBy: " ")
    var result = [Int]()
    for note in notes {
        if note == "o|" {
            result.append(2)
        } else if note == "o" {
            result.append(4)
        } else if note == ".|" {
            result.append(1)
        } else {
            result.append(1)
        }
    }
    return result
}
```

func parseMusic(musicString: String) -> [Int] {
    return []
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    return []
}
```

func parseMusic(musicString: String) -> [Int] {
    return []
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    return []
}
```

func parseMusic(musicString: String) -> [Int] {
    return []
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    return []
}
```

func parseMusic(musicString: String) -> [Int] {
    return []
}

```swift
// Input to this function is a string representing musical notes in a special ASCII format.
// Your task is to parse this string and return array of integers corresponding to how many beats does each
// not last.
// Here is a legend:
// 'o' - whole note, lasts four beats
// 'o|' - half note, lasts two beats
// '.|' - quater note, lasts one beat
// parseMusic(musicString: "o o|.| o| o|.|.|.|.| o o") == [4, 2, 1, 2, 2, 1, 1, 1, 1, 4, 4]
func parseMusic(musicString: String) -> [Int] {
    return []
}
```

func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else {
        return 0
    }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
        }
        index = string.index(after: index)
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else {
        return 0
    }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
        }
        index = string.index(after: index)
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if let range = string.range(of: substring, range: index..<string.endIndex, options:.caseInsensitive) {
            count += 1
            index = range.upperBound
        } else {
            break
        }
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if let range = string.range(of: substring, range: index..<string.endIndex, options:.caseInsensitive) {
            count += 1
            index = range.upperBound
        } else {
            break
        }
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
            index = string.index(after: index)
        } else {
            index = string.index(after: index)
        }
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
            index = string.index(after: index)
        } else {
            index = string.index(after: index)
        }
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
            index = string.index(after: index)
        } else {
            index = string.index(after: index)
        }
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
            index = string.index(after: index)
        } else {
            index = string.index(after: index)
        }
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index] == substring.first! {
            let range = index..<string.index(index, offsetBy: substring.count)
            if string[range] == substring {
                count += 1
                index = range.upperBound
            } else {
                index = string.index(after: index)
            }
        } else {
            index = string.index(after: index)
        }
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    guard!string.isEmpty &&!substring.isEmpty else { return 0 }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index] == substring.first! {
            let range = index..<string.index(index, offsetBy: substring.count)
            if string[range] == substring {
                count += 1
                index = range.upperBound
            } else {
                index = string.index(after: index)
            }
        } else {
            index = string.index(after: index)
        }
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex, let range = string.range(of: substring, range: index..<string.endIndex) {
        index = range.upperBound
        count += 1
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex, let range = string.range(of: substring, range: index..<string.endIndex) {
        index = range.upperBound
        count += 1
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    if string.isEmpty || substring.isEmpty {
        return 0
    }
    
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index] == substring.first! {
            let range = index..<string.index(index, offsetBy: substring.count)
            if string[range] == substring {
                count += 1
            }
        }
        index = string.index(after: index)
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    if string.isEmpty || substring.isEmpty {
        return 0
    }
    
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index] == substring.first! {
            let range = index..<string.index(index, offsetBy: substring.count)
            if string[range] == substring {
                count += 1
            }
        }
        index = string.index(after: index)
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index...].hasPrefix(substring) {
            index = string.index(index, offsetBy: substring.count)
            count += 1
        } else {
            index = string.index(after: index)
        }
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index...].hasPrefix(substring) {
            index = string.index(index, offsetBy: substring.count)
            count += 1
        } else {
            index = string.index(after: index)
        }
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex, let range = string.range(of: substring, range: index..<string.endIndex) {
        index = range.upperBound
        count += 1
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    var count = 0
    var index = string.startIndex
    while index < string.endIndex, let range = string.range(of: substring, range: index..<string.endIndex) {
        index = range.upperBound
        count += 1
    }
    return count
}
```

func howManyTimes(string: String, substring: String) -> Int {
    if string.isEmpty || substring.isEmpty {
        return 0
    }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
        }
        index = string.index(after: index)
    }
    return count
}

```swift
// Find how many times a given substring can be found in the original string. Count overlaping cases.
// howManyTimes(string: "", substring: "a") == 0
// howManyTimes(string: "aaa", substring: "a") == 3
// howManyTimes(string: "aaaa", substring: "aa") == 3
func howManyTimes(string: String, substring: String) -> Int {
    if string.isEmpty || substring.isEmpty {
        return 0
    }
    var count = 0
    var index = string.startIndex
    while index < string.endIndex {
        if string[index..<string.index(after: index)] == substring {
            count += 1
        }
        index = string.index(after: index)
    }
    return count
}
```

func sortNumbers(numbers: String) -> String {
    // Your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Your code here
}
```

func sortNumbers(numbers: String) -> String {
    // Your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Your code here
}
```

func sortNumbers(numbers: String) -> String {
    // Write your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Write your code here
}
```

func sortNumbers(numbers: String) -> String {
    // Your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Your code here
}
```

func sortNumbers(numbers: String) -> String {
    // Your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Your code here
}
```

func sortNumbers(numbers: String) -> String {
    // Your code here
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    // Your code here
}
```

func sortNumbers(numbers: String) -> String {
    let numberArray = numbers.components(separatedBy: " ")
    let sortedArray = numberArray.sorted {
        let firstNumber = Int($0)
        let secondNumber = Int($1)
        return firstNumber! < secondNumber!
    }
    return sortedArray.joined(separator: " ")
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    let numberArray = numbers.components(separatedBy: " ")
    let sortedArray = numberArray.sorted {
        let firstNumber = Int($0)
        let secondNumber = Int($1)
        return firstNumber! < secondNumber!
    }
    return sortedArray.joined(separator: " ")
}
```

func sortNumbers(numbers: String) -> String {
    return numbers.components(separatedBy: " ").sorted().joined(separator: " ")
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    return numbers.components(separatedBy: " ").sorted().joined(separator: " ")
}
```

func sortNumbers(numbers: String) -> String {
    let numbers = numbers.components(separatedBy: " ")
    let sortedNumbers = numbers.sorted { (first, second) -> Bool in
        let firstNumber = Int(first)
        let secondNumber = Int(second)
        return firstNumber! < secondNumber!
    }
    return sortedNumbers.joined(separator: " ")
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    let numbers = numbers.components(separatedBy: " ")
    let sortedNumbers = numbers.sorted { (first, second) -> Bool in
        let firstNumber = Int(first)
        let secondNumber = Int(second)
        return firstNumber! < secondNumber!
    }
    return sortedNumbers.joined(separator: " ")
}
```

func sortNumbers(numbers: String) -> String {
    let numbersArray = numbers.components(separatedBy: " ")
    let sortedNumbersArray = numbersArray.sorted {
        let firstNumber = Int($0)
        let secondNumber = Int($1)
        return firstNumber! < secondNumber!
    }
    return sortedNumbersArray.joined(separator: " ")
}

```swift
// Input is a space-delimited string of numberals from 'zero' to 'nine'.
// Valid choices are 'zero', 'one', 'two', 'three', 'four', 'five','six','seven', 'eight' and 'nine'.
// Return the string with numbers sorted from smallest to largest
// sortNumbers(numbers: "three one five") == "one three five"
func sortNumbers(numbers: String) -> String {
    let numbersArray = numbers.components(separatedBy: " ")
    let sortedNumbersArray = numbersArray.sorted {
        let firstNumber = Int($0)
        let secondNumber = Int($1)
        return firstNumber! < secondNumber!
    }
    return sortedNumbersArray.joined(separator: " ")
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // Your code here
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // Your code here
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
    return (0.0, 0.0)
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
    return (0.0, 0.0)
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    
    return closestElements
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
    return (0, 0)
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    // TODO: Implement this function
    return (0, 0)
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (Double.infinity, Double.infinity)
    var smallestDifference = Double.infinity
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let difference = abs(numbers[i] - numbers[j])
            if difference < smallestDifference {
                smallestDifference = difference
                closestElements = (numbers[i], numbers[j])
            }
        }
    }
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (Double.infinity, Double.infinity)
    var smallestDifference = Double.infinity
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let difference = abs(numbers[i] - numbers[j])
            if difference < smallestDifference {
                smallestDifference = difference
                closestElements = (numbers[i], numbers[j])
            }
        }
    }
    return closestElements
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (numbers[0], numbers[1])
    var closestDistance = abs(numbers[0] - numbers[1])
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < closestDistance {
                closestElements = (numbers[i], numbers[j])
                closestDistance = distance
            }
        }
    }
    return closestElements
}
```

func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (Double.infinity, Double.infinity)
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < abs(closestElements.0 - closestElements.1) {
                closestElements = (numbers[i], numbers[j])
            }
        }
    }
    return closestElements
}

```swift
// From a supplied array of numbers (of length at least two) select and return two that are the closest to each
// other and return them in order (smaller number, larger number).
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.2]) == (2.0, 2.2)
// findClosestElements(numbers: [1.0, 2.0, 3.0, 4.0, 5.0, 2.0]) == (2.0, 2.0)
func findClosestElements(numbers: [Double]) -> (Double, Double) {
    var closestElements = (Double.infinity, Double.infinity)
    for i in 0..<numbers.count {
        for j in i+1..<numbers.count {
            let distance = abs(numbers[i] - numbers[j])
            if distance < abs(closestElements.0 - closestElements.1) {
                closestElements = (numbers[i], numbers[j])
            }
        }
    }
    return closestElements
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Implement this function
    return []
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let diff = max - min
    return numbers.map { ($0 - min) / diff }
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let diff = max - min
    return numbers.map { ($0 - min) / diff }
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: implement this function
    return []
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: implement this function
    return []
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    return numbers.map { ($0 - min) / (max - min) }
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    return numbers.map { ($0 - min) / (max - min) }
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let range = max - min
    return numbers.map { ($0 - min) / range }
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let range = max - min
    return numbers.map { ($0 - min) / range }
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Your code here
    return []
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    // TODO: Your code here
    return []
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    return numbers.map { ($0 - min) / (max - min) }
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    return numbers.map { ($0 - min) / (max - min) }
}
```

func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let diff = max - min
    return numbers.map { ($0 - min) / diff }
}

```swift
// Given array of numbers (of at least two elements), apply a linear transform to that array,
// such that the smallest number will become 0 and the largest will become 1
// rescaleToUnit(numbers: [1.0, 2.0, 3.0, 4.0, 5.0]) == [0.0, 0.25, 0.5, 0.75, 1.0]
func rescaleToUnit(numbers: [Double]) -> [Double] {
    let min = numbers.min()!
    let max = numbers.max()!
    let diff = max - min
    return numbers.map { ($0 - min) / diff }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.compactMap { $0 as? Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    // TODO: Implement this function
    return []
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    // TODO: Implement this function
    return []
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int }.map { $0 as! Int }
}
```

func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int } as! [Int]
}

```swift
// Filter given array of any swiftthon values only for integers
// filterIntegers(values: ["a", 3.14, 5]) == [5]
// filterIntegers(values: [1, 2, 3, "abc", [:] as [AnyHashable : AnyHashable], [] as [AnyHashable]]) == [1, 2, 3]
func filterIntegers(values: [AnyHashable]) -> [Int] {
    return values.filter { $0 is Int } as! [Int]
}
```

func strlen(string: String) -> Int {
    return string.characters.count
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return string.characters.count
}
```

func strlen(string: String) -> Int {
    return 0
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return 0
}
```

func strlen(string: String) -> Int {
    // TODO: Implement this function
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    // TODO: Implement this function
}
```

func strlen(string: String) -> Int {
    return 0
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return 0
}
```

func strlen(string: String) -> Int {
    return 0
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return 0
}
```

func strlen(string: String) -> Int {
    // TODO: Implement strlen
    return 0
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    // TODO: Implement strlen
    return 0
}
```

func strlen(string: String) -> Int {
    return string.count
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return string.count
}
```

func strlen(string: String) -> Int {
    return 0
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return 0
}
```

func strlen(string: String) -> Int {
    return string.count
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return string.count
}
```

func strlen(string: String) -> Int {
    return string.count
}

```swift
// Return length of given string
// strlen(string: "") == 0
// strlen(string: "abc") == 3
func strlen(string: String) -> Int {
    return string.count
}
```

func largestDivisor(n: Int) -> Int {
    // Your code here
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // Your code here
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Your code here
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Your code here
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Write your code here
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Write your code here
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Write your code here
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Write your code here
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Implement this function
    return 0
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Implement this function
    return 0
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Implement
    return 0
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Implement
    return 0
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Implement this function
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Implement this function
}
```

func largestDivisor(n: Int) -> Int {
    // TODO: Implement largestDivisor
    return 0
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    // TODO: Implement largestDivisor
    return 0
}
```

func largestDivisor(n: Int) -> Int {
    for i in (1...n).reversed() {
        if n % i == 0 {
            return i
        }
    }
    return 0
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    for i in (1...n).reversed() {
        if n % i == 0 {
            return i
        }
    }
    return 0
}
```

func largestDivisor(n: Int) -> Int {
    var largestDivisor = 0
    for i in 1...n {
        if n % i == 0 {
            largestDivisor = i
        }
    }
    return largestDivisor
}

func smallestDivisor(n: Int) -> Int {
    var smallestDivisor = 0
    for i in n...n*n {
        if i % n == 0 {
            smallestDivisor = i
            break
        }
    }
    return smallestDivisor
}

func sumOfDivisors(n: Int) -> Int {
    var sum = 0
    for i in 1...n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

func numberOfDivisors(n: Int) -> Int {
    var count = 0
    for i in 1...n {
        if n % i == 0 {
            count += 1
        }
    }
    return count
}

func sumOfDivisorsSmallerThanN(n: Int) -> Int {
    var sum = 0
    for i in 1..<n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

func sumOfDivisorsLargerThanN(n: Int) -> Int {
    var sum = 0
    for i in n+1...n*n {
        if i % n == 0 {
            sum += i
        }
    }
    return sum
}

```swift
// For a given number n, find the largest number that divides n evenly, smaller than n
// largestDivisor(n: 15) == 5
func largestDivisor(n: Int) -> Int {
    var largestDivisor = 0
    for i in 1...n {
        if n % i == 0 {
            largestDivisor = i
        }
    }
    return largestDivisor
}

// For a given number n, find the smallest number that divides n evenly, larger than n
// smallestDivisor(n: 15) == 16
func smallestDivisor(n: Int) -> Int {
    var smallestDivisor = 0
    for i in n...n*n {
        if i % n == 0 {
            smallestDivisor = i
            break
        }
    }
    return smallestDivisor
}

// For a given number n, find the sum of all the divisors of n
// sumOfDivisors(n: 15) == 24
func sumOfDivisors(n: Int) -> Int {
    var sum = 0
    for i in 1...n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the number of divisors of n
// numberOfDivisors(n: 15) == 4
func numberOfDivisors(n: Int) -> Int {
    var count = 0
    for i in 1...n {
        if n % i == 0 {
            count += 1
        }
    }
    return count
}

// For a given number n, find the sum of all the divisors of n that are smaller than n
// sumOfDivisorsSmallerThanN(n: 15) == 15
func sumOfDivisorsSmallerThanN(n: Int) -> Int {
    var sum = 0
    for i in 1..<n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are larger than n
// sumOfDivisorsLargerThanN(n: 15) == 16
func sumOfDivisorsLargerThanN(n: Int) -> Int {
    var sum = 0
    for i in n+1...n*n {
        if i % n == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are smaller than n
// sumOfDivisorsSmallerThanN(n: 15) == 15
func sumOfDivisorsSmallerThanN(n: Int) -> Int {
    var sum = 0
    for i in 1..<n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are larger than n
// sumOfDivisorsLargerThanN(n: 15) == 16
func sumOfDivisorsLargerThanN(n: Int) -> Int {
    var sum = 0
    for i in n+1...n*n {
        if i % n == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are smaller than n
// sumOfDivisorsSmallerThanN(n: 15) == 15
func sumOfDivisorsSmallerThanN(n: Int) -> Int {
    var sum = 0
    for i in 1..<n {
        if n % i == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are larger than n
// sumOfDivisorsLargerThanN(n: 15) == 16
func sumOfDivisorsLargerThanN(n: Int) -> Int {
    var sum = 0
    for i in n+1...n*n {
        if i % n == 0 {
            sum += i
        }
    }
    return sum
}

// For a given number n, find the sum of all the divisors of n that are smaller than n
// sumOfDivisorsSmallerThanN(n: 15) == 15
func sumOfDivisorsSmallerThanN(n: Int) -> Int {
    var sum = 0
    for i in 

func factorize(n: Int) -> [Int] {
    // Your code here
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    // Your code here
}
```

func factorize(n: Int) -> [Int] {
    // Your code here
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    // Your code here
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    // your code here
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    // your code here
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while number > 1 {
        while number % i == 0 {
            result.append(i)
            number /= i
        }
        i += 1
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while number > 1 {
        while number % i == 0 {
            result.append(i)
            number /= i
        }
        i += 1
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var i = 2
    while i * i <= number {
        if number % i == 0 {
            result.append(i)
            number /= i
        } else {
            i += 1
        }
    }
    if number > 1 {
        result.append(number)
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}
```

func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}

```swift
// Return array of prime factors of given integer in the order from smallest to largest.
// Each of the factors should be arrayed number of times corresponding to how many times it appeares in factorization.
// Input number should be equal to the product of all factors
// factorize(n: 8) == [2, 2, 2]
// factorize(n: 25) == [5, 5]
// factorize(n: 70) == [2, 5, 7]
func factorize(n: Int) -> [Int] {
    var result = [Int]()
    var number = n
    var divisor = 2
    while number > 1 {
        if number % divisor == 0 {
            result.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var seen = Set<Int>()
    var result = [Int]()
    for number in numbers {
        if!seen.contains(number) {
            seen.insert(number)
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var seen = Set<Int>()
    var result = [Int]()
    for number in numbers {
        if!seen.contains(number) {
            seen.insert(number)
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            result.append(number)
            set.insert(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            result.append(number)
            set.insert(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var dict = [Int: Int]()
    for number in numbers {
        if dict[number] == nil {
            dict[number] = 1
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var dict = [Int: Int]()
    for number in numbers {
        if dict[number] == nil {
            dict[number] = 1
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            result.append(number)
            set.insert(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            result.append(number)
            set.insert(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var result = [Int]()
    var set = Set<Int>()
    for number in numbers {
        if!set.contains(number) {
            set.insert(number)
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var dict = [Int: Int]()
    var result = [Int]()
    for number in numbers {
        if dict[number] == nil {
            dict[number] = 1
            result.append(number)
        }
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var dict = [Int: Int]()
    var result = [Int]()
    for number in numbers {
        if dict[number] == nil {
            dict[number] = 1
            result.append(number)
        }
    }
    return result
}
```

func removeDuplicates(numbers: [Int]) -> [Int] {
    var seen = Set<Int>()
    var result = [Int]()
    for number in numbers {
        if seen.contains(number) {
            continue
        }
        seen.insert(number)
        result.append(number)
    }
    return result
}

```swift
// From an array of integers, remove all elements that occur more than once.
// Keep order of elements left the same as in the input.
// removeDuplicates(numbers: [1, 2, 3, 2, 4]) == [1, 3, 4]
func removeDuplicates(numbers: [Int]) -> [Int] {
    var seen = Set<Int>()
    var result = [Int]()
    for number in numbers {
        if seen.contains(number) {
            continue
        }
        seen.insert(number)
        result.append(number)
    }
    return result
}
```

func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char).lowercased()
        } else {
            result += String(char).uppercased()
        }
    }
    return result
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char).lowercased()
        } else {
            result += String(char).uppercased()
        }
    }
    return result
}
```

func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char.lowercased())
        } else {
            result += String(char.uppercased())
        }
    }
    return result
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char.lowercased())
        } else {
            result += String(char.uppercased())
        }
    }
    return result
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isLowercase {
            newString.append(String(char).uppercased())
        } else {
            newString.append(String(char).lowercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isLowercase {
            newString.append(String(char).uppercased())
        } else {
            newString.append(String(char).lowercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isLowercase {
            newString.append(String(char).uppercased())
        } else {
            newString.append(String(char).lowercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isLowercase {
            newString.append(String(char).uppercased())
        } else {
            newString.append(String(char).lowercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char).lowercased()
        } else {
            result += String(char).uppercased()
        }
    }
    return result
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var result = ""
    for char in string.characters {
        if char.isUppercase {
            result += String(char).lowercased()
        } else {
            result += String(char).uppercased()
        }
    }
    return result
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString += String(char.lowercased())
        } else {
            newString += String(char.uppercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString += String(char.lowercased())
        } else {
            newString += String(char.uppercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    var newString = ""
    for char in string.characters {
        if char.isUppercase {
            newString.append(char.lowercased())
        } else {
            newString.append(char.uppercased())
        }
    }
    return newString
}
```

func flipCase(string: String) -> String {
    return string.map {
        if $0.isUppercase {
            return $0.lowercased()
        } else {
            return $0.uppercased()
        }
    }.joined()
}

```swift
// For a given string, flip lowercase characters to uppercase and uppercase to lowercase.
// flipCase(string: "Hello") == "hELLO"
func flipCase(string: String) -> String {
    return string.map {
        if $0.isUppercase {
            return $0.lowercased()
        } else {
            return $0.uppercased()
        }
    }.joined()
}
```

func concatenate(strings: [String]) -> String {
    // TODO: Your code here
    return ""
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    // TODO: Your code here
    return ""
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", { $0 + $1 })
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", { $0 + $1 })
}
```

func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}

```swift
// Concatenate array of strings into a single string
// concatenate(strings: [] as [String]) == ""
// concatenate(strings: ["a", "b", "c"]) == "abc"
func concatenate(strings: [String]) -> String {
    return strings.reduce("", +)
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}

```swift
// Filter an input array of strings only for ones that start with a given prefix.
// filterByPrefix(strings: [] as [String], prefix: "a") == [] as [String]
// filterByPrefix(strings: ["abc", "bcd", "cde", "array"], prefix: "a") == ["abc", "array"]
func filterByPrefix(strings: [String], prefix: String) -> [String] {
    return strings.filter { $0.hasPrefix(prefix) }
}
```

func getPositive(l: [Int]) -> [Int] {
    // TODO: Write your code here.
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    // TODO: Write your code here.
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter { $0 > 0 }
}
```

func getPositive(l: [Int]) -> [Int] {
    return l.filter({ $0 > 0 })
}

```swift
// Return only positive numbers in the array.
// getPositive(l: [-1, 2, -4, 5, 6]) == [2, 5, 6]
// getPositive(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == [5, 3, 2, 3, 9, 123, 1]
func getPositive(l: [Int]) -> [Int] {
    return l.filter({ $0 > 0 })
}
```

func isPrime(n: Int) -> Bool {
    // your code here
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    // your code here
}
```

func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    if n == 2 {
        return true
    }
    for i in 2...Int(sqrt(Double(n))) {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    if n == 2 {
        return true
    }
    for i in 2...Int(sqrt(Double(n))) {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    var i = 3
    while i * i <= n {
        if n % i == 0 {
            return false
        }
        i += 2
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    var i = 3
    while i * i <= n {
        if n % i == 0 {
            return false
        }
        i += 2
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    var i = 3
    while i * i <= n {
        if n % i == 0 {
            return false
        }
        i += 2
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    var i = 3
    while i * i <= n {
        if n % i == 0 {
            return false
        }
        i += 2
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// Return true if a given number is prime, and false otherwise.
// isPrime(n: 6) == false
// isPrime(n: 101) == true
// isPrime(n: 11) == true
// isPrime(n: 13441) == true
// isPrime(n: 61) == true
// isPrime(n: 4) == false
// isPrime(n: 1) == false
func isPrime(n: Int) -> Bool {
    if n == 1 {
        return false
    }
    for i in 2..<n {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i...].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i...].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
// to the values of the corresponding indicies of l, but sorted.
// sortThird(l: [1, 2, 3]) == [1, 2, 3]
// sortThird(l: [5, 6, 3, 4, 8, 9, 2]) == [2, 6, 3, 4, 8, 9, 5]
func sortThird(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 3 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort()
}
```

func unique(l: [Int]) -> [Int] {
    var seen = Set<Int>()
    return l.filter {
        if seen.contains($0) {
            return false
        } else {
            seen.insert($0)
            return true
        }
    }
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    var seen = Set<Int>()
    return l.filter {
        if seen.contains($0) {
            return false
        } else {
            seen.insert($0)
            return true
        }
    }
}
```

func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort(<)
}

```swift
// Return sorted unique elements in an array
// unique(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [0, 2, 3, 5, 9, 123]
func unique(l: [Int]) -> [Int] {
    return Array(Set(l)).sort(<)
}
```

func maxElement(l: [Int]) -> Int {
    // TODO: Implement this function.
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    // TODO: Implement this function.
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 0..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 0..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in l {
        if i > max {
            max = i
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in l {
        if i > max {
            max = i
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 0..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 0..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in l {
        if i > max {
            max = i
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in l {
        if i > max {
            max = i
        }
    }
    return max
}
```

func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}

```swift
// Return maximum element in the array.
// maxElement(l: [1, 2, 3]) == 3
// maxElement(l: [5, 3, -5, 2, -3, 3, 9, 0, 123, 1, -10]) == 123
func maxElement(l: [Int]) -> Int {
    var max = l[0]
    for i in 1..<l.count {
        if l[i] > max {
            max = l[i]
        }
    }
    return max
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for j in str {
                if j == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for j in str {
                if j == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var temp = i
            while temp > 0 {
                if temp % 10 == 7 {
                    count += 1
                }
                temp /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var temp = i
            while temp > 0 {
                if temp % 10 == 7 {
                    count += 1
                }
                temp /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var temp = i
            while temp > 0 {
                if temp % 10 == 7 {
                    count += 1
                }
                temp /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var temp = i
            while temp > 0 {
                if temp % 10 == 7 {
                    count += 1
                }
                temp /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for c in str {
                if c == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for c in str {
                if c == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for c in str {
                if c == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            let str = String(i)
            for c in str {
                if c == "7" {
                    count += 1
                }
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}
```

func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}

```swift
// Return the number of times the digit 7 appears in integers less than n which are divisible by 11 or 13.
// fizzBuzz(n: 50) == 0
// fizzBuzz(n: 78) == 2
// fizzBuzz(n: 79) == 3
func fizzBuzz(n: Int) -> Int {
    var count = 0
    for i in 1..<n {
        if i % 11 == 0 || i % 13 == 0 {
            var num = i
            while num > 0 {
                if num % 10 == 7 {
                    count += 1
                }
                num /= 10
            }
        }
    }
    return count
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    // TODO: implement this function
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    // TODO: implement this function
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[i / 2]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l.sorted()[i]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l.sorted()[i]
        }
    }
    return l
}
```

func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}

```swift
// This function takes an array l and returns an array l' such that
// l' is identical to l in the odd indicies, while its values at the even indicies are equal
// to the values of the even indicies of l, but sorted.
// sortEven(l: [1, 2, 3]) == [1, 2, 3]
// sortEven(l: [5, 6, 3, 4]) == [3, 6, 5, 4]
func sortEven(l: [Int]) -> [Int] {
    var l = l
    for i in 0..<l.count {
        if i % 2 == 0 {
            l[i] = l[i..<l.count].sorted()[0]
        }
    }
    return l
}
```

func primeFib(n: Int) -> Int {
    var fib = [1, 1]
    var i = 2
    while true {
        let next = fib[i - 1] + fib[i - 2]
        if next.isPrime() {
            fib.append(next)
            if fib.count == n {
                return next
            }
        }
        i += 1
    }
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    var fib = [1, 1]
    var i = 2
    while true {
        let next = fib[i - 1] + fib[i - 2]
        if next.isPrime() {
            fib.append(next)
            if fib.count == n {
                return next
            }
        }
        i += 1
    }
}
```

func primeFib(n: Int) -> Int {
    // your code here
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    // your code here
}
```

func primeFib(n: Int) -> Int {
    // your code here
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    // your code here
}
```

func primeFib(n: Int) -> Int {
    return 0
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    return 0
}
```

func primeFib(n: Int) -> Int {
    // your code here
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    // your code here
}
```

func primeFib(n: Int) -> Int {
    // your code here
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    // your code here
}
```

func primeFib(n: Int) -> Int {
    // your code here
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    // your code here
}
```

func primeFib(n: Int) -> Int {
    var fib = [0, 1]
    var i = 2
    while true {
        let next = fib[i - 1] + fib[i - 2]
        if next > 1000000000 {
            break
        }
        fib.append(next)
        i += 1
    }
    var primes = [Int]()
    for i in 0..<fib.count {
        if isPrime(fib[i]) {
            primes.append(fib[i])
        }
    }
    return primes[n - 1]
}

func isPrime(_ n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    for i in stride(from: 3, through: Int(sqrt(Double(n))), by: 2) {
        if n % i == 0 {
            return false
        }
    }
    return true
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    var fib = [0, 1]
    var i = 2
    while true {
        let next = fib[i - 1] + fib[i - 2]
        if next > 1000000000 {
            break
        }
        fib.append(next)
        i += 1
    }
    var primes = [Int]()
    for i in 0..<fib.count {
        if isPrime(fib[i]) {
            primes.append(fib[i])
        }
    }
    return primes[n - 1]
}

func isPrime(_ n: Int) -> Bool {
    if n <= 1 {
        return false
    }
    if n == 2 {
        return true
    }
    if n % 2 == 0 {
        return false
    }
    for i in stride(from: 3, through: Int(sqrt(Double(n))), by: 2) {
        if n % i == 0 {
            return false
        }
    }
    return true
}
```

func primeFib(n: Int) -> Int {
    return 0
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    return 0
}
```

func primeFib(n: Int) -> Int {
    return 0
}

```swift
// prime_fib returns n-th number that is a Fibonacci number and it's also prime.
// primeFib(n: 1) == 2
// primeFib(n: 2) == 3
// primeFib(n: 3) == 5
// primeFib(n: 4) == 13
// primeFib(n: 5) == 89
func primeFib(n: Int) -> Int {
    return 0
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}
```

func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Implement this function.
    return false
}

```swift
// triples_sum_to_zero takes an array of integers as an input.
// it returns true if there are three distinct elements in the array that
// sum to zero, and false otherwise.
// triplesSumToZero(l: [1, 3, 5, 0]) == false
// triplesSumToZero(l: [1, 3, -2, 1]) == true
// triplesSumToZero(l: [1, 2, 3, 7]) == false
// triplesSumToZero(l: [2, 4, -5, 3, 9, 7]) == true
// triplesSumToZero(l: [1]) == false
func triplesSumToZero(l: [Int]) -> Bool {
    // TODO: Implement this function.
    return false
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: Implement this function.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: Implement this function.
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: Implement this function.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: Implement this function.
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here.
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: implement this function
}
```

func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // TODO: Write your code here.
}
```

func carRaceCollision(n: Int) -> Int {
    // Write your code here.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // Write your code here.
}
```

func carRaceCollision(n: Int) -> Int {
    // Write your code here.
}

```swift
// Imagine a road that's a perfectly straight infinitely long line.
// n cars are driving left to right;  simultaneously, a different set of n cars
// are driving right to left.   The two sets of cars start out being very far from
// each other.  All cars move in the same speed.  Two cars are said to collide
// when a car that's moving left to right hits a car that's moving right to left.
// However, the cars are infinitely sturdy and strong; as a result, they continue moving
// in their trajectory as if they did not collide.
// This function outputs the number of such collisions.
func carRaceCollision(n: Int) -> Int {
    // Write your code here.
}
```

func incrList(l: [Int]) -> [Int] {
    // TODO: implement this function
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    // TODO: implement this function
}
```

func incrList(l: [Int]) -> [Int] {
    var newList = [Int]()
    for i in l {
        newList.append(i + 1)
    }
    return newList
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    var newList = [Int]()
    for i in l {
        newList.append(i + 1)
    }
    return newList
}
```

func incrList(l: [Int]) -> [Int] {
    var newList: [Int] = []
    for i in l {
        newList.append(i + 1)
    }
    return newList
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    var newList: [Int] = []
    for i in l {
        newList.append(i + 1)
    }
    return newList
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func incrList(l: [Int]) -> [Int] {
    var newList = [Int]()
    for i in l {
        newList.append(i + 1)
    }
    return newList
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    var newList = [Int]()
    for i in l {
        newList.append(i + 1)
    }
    return newList
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}

```swift
// Return array with elements incremented by 1.
// incrList(l: [1, 2, 3]) == [2, 3, 4]
// incrList(l: [5, 3, 5, 2, 3, 3, 9, 0, 123]) == [6, 4, 6, 3, 4, 4, 10, 1, 124]
func incrList(l: [Int]) -> [Int] {
    return l.map { $0 + 1 }
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: your code here
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // your code here
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // your code here
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: implement this function
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: write your code here
    return false
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: write your code here
    return false
}
```

func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}

```swift
// pairs_sum_to_zero takes an array of integers as an input.
// it returns true if there are two distinct elements in the array that
// sum to zero, and false otherwise.
// pairsSumToZero(l: [1, 3, 5, 0]) == false
// pairsSumToZero(l: [1, 3, -2, 1]) == false
// pairsSumToZero(l: [1, 2, 3, 7]) == false
// pairsSumToZero(l: [2, 4, -5, 3, 5, 7]) == true
// pairsSumToZero(l: [1]) == false
func pairsSumToZero(l: [Int]) -> Bool {
    // TODO: Write your code here
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: Implement this function.
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: Implement this function.
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: Your code here
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: Your code here
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: Write your code here
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: Write your code here
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: Write your code here.
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: Write your code here.
}
```

func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var num = x
    while num > 0 {
        result = String(num % base) + result
        num /= base
    }
    return result
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var num = x
    while num > 0 {
        result = String(num % base) + result
        num /= base
    }
    return result
}
```

func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var num = x
    while num > 0 {
        result = String(num % base) + result
        num /= base
    }
    return result
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var num = x
    while num > 0 {
        result = String(num % base) + result
        num /= base
    }
    return result
}
```

func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var x = x
    while x > 0 {
        result = "\(x % base)" + result
        x /= base
    }
    return result
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var x = x
    while x > 0 {
        result = "\(x % base)" + result
        x /= base
    }
    return result
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: implement this function
    return ""
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: implement this function
    return ""
}
```

func changeBase(x: Int, base: Int) -> String {
    // TODO: implement
    return ""
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    // TODO: implement
    return ""
}
```

func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var x = x
    while x > 0 {
        result = String(x % base) + result
        x /= base
    }
    return result
}

```swift
// Change numerical base of input number x to base.
// return string representation after the conversion.
// base numbers are less than 10.
// changeBase(x: 8, base: 3) == "22"
// changeBase(x: 8, base: 2) == "1000"
// changeBase(x: 7, base: 2) == "111"
func changeBase(x: Int, base: Int) -> String {
    var result = ""
    var x = x
    while x > 0 {
        result = String(x % base) + result
        x /= base
    }
    return result
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}

```swift
// Given length of a side and high return area for a triangle.
// triangleArea(a: 5, h: 3) == 7.5
func triangleArea(a: Int, h: Int) -> Double {
    return Double(a * h) / 2
}
```

func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
    }
    return fib4Array[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
    }
    return fib4Array[n]
}
```

func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}
```

func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        let fib4 = fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4]
        fib4Array.append(fib4)
    }
    return fib4Array[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        let fib4 = fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4]
        fib4Array.append(fib4)
    }
    return fib4Array[n]
}
```

func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    if n < 4 {
        return fib4[n]
    }
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    if n < 4 {
        return fib4[n]
    }
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}
```

func fib4(n: Int) -> Int {
    var fib4 = [Int](repeating: 0, count: n + 1)
    fib4[1] = 0
    fib4[2] = 2
    fib4[3] = 0
    for i in 4...n {
        fib4[i] = fib4[i - 1] + fib4[i - 2] + fib4[i - 3] + fib4[i - 4]
    }
    return fib4[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4 = [Int](repeating: 0, count: n + 1)
    fib4[1] = 0
    fib4[2] = 2
    fib4[3] = 0
    for i in 4...n {
        fib4[i] = fib4[i - 1] + fib4[i - 2] + fib4[i - 3] + fib4[i - 4]
    }
    return fib4[n]
}
```

func fib4(n: Int) -> Int {
    if n < 2 {
        return 0
    } else if n == 2 {
        return 2
    } else {
        var fib4Array = [0, 0, 2]
        for i in 3...n {
            let fib4 = fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4]
            fib4Array.append(fib4)
        }
        return fib4Array[n]
    }
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    if n < 2 {
        return 0
    } else if n == 2 {
        return 2
    } else {
        var fib4Array = [0, 0, 2]
        for i in 3...n {
            let fib4 = fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4]
            fib4Array.append(fib4)
        }
        return fib4Array[n]
    }
}
```

func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    if n < 4 {
        return fib4[n]
    }
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4 = [0, 0, 2, 0]
    if n < 4 {
        return fib4[n]
    }
    for i in 4...n {
        fib4.append(fib4[i-1] + fib4[i-2] + fib4[i-3] + fib4[i-4])
    }
    return fib4[n]
}
```

func fib4(n: Int) -> Int {
    if n < 2 {
        return 0
    } else if n == 2 {
        return 2
    } else if n == 3 {
        return 0
    } else {
        var fib4Array = [0, 0, 2, 0]
        for i in 4...n {
            fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
        }
        return fib4Array[n]
    }
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    if n < 2 {
        return 0
    } else if n == 2 {
        return 2
    } else if n == 3 {
        return 0
    } else {
        var fib4Array = [0, 0, 2, 0]
        for i in 4...n {
            fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
        }
        return fib4Array[n]
    }
}
```

func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        let newFib4 = fib4Array[0] + fib4Array[1] + fib4Array[2] + fib4Array[3]
        fib4Array.removeFirst()
        fib4Array.append(newFib4)
    }
    return fib4Array.last!
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        let newFib4 = fib4Array[0] + fib4Array[1] + fib4Array[2] + fib4Array[3]
        fib4Array.removeFirst()
        fib4Array.append(newFib4)
    }
    return fib4Array.last!
}
```

func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
    }
    return fib4Array[n]
}

```swift
// The Fib4 number sequence is a sequence similar to the Fibbonacci sequnece that's defined as follows:
// fib4(0) -> 0
// fib4(1) -> 0
// fib4(2) -> 2
// fib4(3) -> 0
// fib4(n) -> fib4(n-1) + fib4(n-2) + fib4(n-3) + fib4(n-4).
// Please write a function to efficiently compute the n-th element of the fib4 number sequence.  Do not use recursion.
// fib4(n: 5) == 4
// fib4(n: 6) == 8
// fib4(n: 7) == 14
func fib4(n: Int) -> Int {
    var fib4Array = [0, 0, 2, 0]
    if n < 4 {
        return fib4Array[n]
    }
    for i in 4...n {
        fib4Array.append(fib4Array[i-1] + fib4Array[i-2] + fib4Array[i-3] + fib4Array[i-4])
    }
    return fib4Array[n]
}
```

func median(l: [Int]) -> Double {
    // TODO: your code here
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    // TODO: your code here
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let mid = sorted.count / 2
    if sorted.count % 2 == 0 {
        return Double(sorted[mid] + sorted[mid - 1]) / 2
    } else {
        return Double(sorted[mid])
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let mid = sorted.count / 2
    if sorted.count % 2 == 0 {
        return Double(sorted[mid] + sorted[mid - 1]) / 2
    } else {
        return Double(sorted[mid])
    }
}
```

func median(l: [Int]) -> Double {
    // TODO: Implement this function.
    return 0.0
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    // TODO: Implement this function.
    return 0.0
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n/2])
    } else {
        return Double(sorted[n/2 - 1] + sorted[n/2]) / 2.0
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n/2])
    } else {
        return Double(sorted[n/2 - 1] + sorted[n/2]) / 2.0
    }
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 0 {
        return Double(sorted[count / 2 - 1] + sorted[count / 2]) / 2
    } else {
        return Double(sorted[count / 2])
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 0 {
        return Double(sorted[count / 2 - 1] + sorted[count / 2]) / 2
    } else {
        return Double(sorted[count / 2])
    }
}
```

func median(l: [Int]) -> Double {
    // TODO: Implement this function.
    return 0.0
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    // TODO: Implement this function.
    return 0.0
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n / 2])
    } else {
        return Double(sorted[n / 2 - 1] + sorted[n / 2]) / 2.0
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n / 2])
    } else {
        return Double(sorted[n / 2 - 1] + sorted[n / 2]) / 2.0
    }
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 0 {
        let middle = count / 2
        return Double(sorted[middle] + sorted[middle - 1]) / 2.0
    } else {
        return Double(sorted[count / 2])
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 0 {
        let middle = count / 2
        return Double(sorted[middle] + sorted[middle - 1]) / 2.0
    } else {
        return Double(sorted[count / 2])
    }
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 1 {
        return Double(sorted[count / 2])
    } else {
        let a = sorted[count / 2 - 1]
        let b = sorted[count / 2]
        return Double(a + b) / 2
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let count = sorted.count
    if count % 2 == 1 {
        return Double(sorted[count / 2])
    } else {
        let a = sorted[count / 2 - 1]
        let b = sorted[count / 2]
        return Double(a + b) / 2
    }
}
```

func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n / 2])
    } else {
        return Double(sorted[n / 2 - 1] + sorted[n / 2]) / 2.0
    }
}

```swift
// Return median of elements in the array l.
// median(l: [3, 1, 2, 4, 5]) == 3
// median(l: [-10, 4, 6, 1000, 10, 20]) == 15.0
func median(l: [Int]) -> Double {
    let sorted = l.sorted()
    let n = sorted.count
    if n % 2 == 1 {
        return Double(sorted[n / 2])
    } else {
        return Double(sorted[n / 2 - 1] + sorted[n / 2]) / 2.0
    }
}
```

func isPalindrome(text: String) -> Bool {
    if text.isEmpty {
        return true
    }
    
    let first = text.first!
    let last = text.last!
    
    if first!= last {
        return false
    }
    
    let middle = text.dropFirst().dropLast()
    return isPalindrome(text: String(middle))
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    if text.isEmpty {
        return true
    }
    
    let first = text.first!
    let last = text.last!
    
    if first!= last {
        return false
    }
    
    let middle = text.dropFirst().dropLast()
    return isPalindrome(text: String(middle))
}
```

func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}
```

func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
    return false
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
    return false
}
```

func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}
```

func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
}
```

func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
    return false
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    // TODO: Implement this function
    return false
}
```

func isPalindrome(text: String) -> Bool {
    let reversed = String(text.reversed())
    return text == reversed
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    let reversed = String(text.reversed())
    return text == reversed
}
```

func isPalindrome(text: String) -> Bool {
    guard text.count > 1 else { return true }
    let first = text.first!
    let last = text.last!
    let middle = text.dropFirst().dropLast()
    return first == last && isPalindrome(text: String(middle))
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    guard text.count > 1 else { return true }
    let first = text.first!
    let last = text.last!
    let middle = text.dropFirst().dropLast()
    return first == last && isPalindrome(text: String(middle))
}
```

func isPalindrome(text: String) -> Bool {
    guard text.count > 1 else {
        return true
    }

    let firstCharacter = text.first!
    let lastCharacter = text.last!

    if firstCharacter == lastCharacter {
        let substring = text.dropFirst().dropLast()
        return isPalindrome(text: String(substring))
    } else {
        return false
    }
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    guard text.count > 1 else {
        return true
    }

    let firstCharacter = text.first!
    let lastCharacter = text.last!

    if firstCharacter == lastCharacter {
        let substring = text.dropFirst().dropLast()
        return isPalindrome(text: String(substring))
    } else {
        return false
    }
}
```

func isPalindrome(text: String) -> Bool {
    let text = text.lowercased()
    let reversedText = String(text.reversed())
    return text == reversedText
}

```swift
// Checks if given string is a palindrome
// isPalindrome(text: "") == true
// isPalindrome(text: "aba") == true
// isPalindrome(text: "aaaaa") == true
// isPalindrome(text: "zbcd") == false
func isPalindrome(text: String) -> Bool {
    let text = text.lowercased()
    let reversedText = String(text.reversed())
    return text == reversedText
}
```

func modp(n: Int, p: Int) -> Int {
    // TODO: implement
    return 0
}

```swift
// Return 2^n modulo p (be aware of numerics).
// modp(n: 3, p: 5) == 3
// modp(n: 1101, p: 101) == 2
// modp(n: 0, p: 101) == 1
// modp(n: 3, p: 11) == 8
// modp(n: 100, p: 101) == 1
func modp(n: Int, p: Int) -> Int {
    // TODO: implement
    return 0
}
```