in swift

func riddle(arr: [Int]) -> [Int] {
    let n = arr.count
    var maxWin = [Int](repeating: 0, count: n)
    var stack = [(index: Int, value: Int)]()
    var leftBoundaries = [Int](repeating: 0, count: n)
    var rightBoundaries = [Int](repeating: n, count: n)

     for i in 0..<n {
         while !stack.isEmpty && stack.last!.value >= arr[i] {
                stack.popLast()
            }
    leftBoundaries[i] = stack.isEmpty ? 0 : stack.last!.index + 1
    stack.append((index: i, value: arr[i]))
        }

stack.removeAll()

for i in stride(from: n - 1, through: 0, by: -1) {
        while !stack.isEmpty && stack.last!.value >= arr[i] {
            stack.popLast()
  }
  rightBoundaries[i] = stack.isEmpty ? n : stack.last!.index
  stack.append((index: i, value: arr[i]))
}

for i in 0..<n {
        let windowSize = rightBoundaries[i] - leftBoundaries[i]
  maxWin[windowSize - 1] = max(maxWin[windowSize - 1], arr[i])
}

for i in stride(from: n - 2, through: 0, by: -1) {
        maxWin[i] = max(maxWin[i], maxWin[i + 1])
}

        return maxWin
}