qs.swift

func quicksort(inout list:[Int], var left:Int = -1, var right:Int = -1) {
    if left == -1 && right == -1 {
        left = 0
        right = list.count - 1
    }
    
    func partition(left:Int, right:Int) -> Int {
        var i = left
        
        for j in left+1...right {
            if list[j] < list[left] {
                i++
                
                (list[i], list[j]) = (list[j], list[i])
            }
        }
        
        (list[i], list[left]) = (list[left], list[i])
        return i
    }
    
    if right > left {
        let pivotIndex = partition(left, right)
        quicksort(&list, left: left, right: pivotIndex - 1)
        quicksort(&list, left: pivotIndex + 1, right: right)
    }
}

func quicksort(inout list:[Int], var left:Int = -1, var right:Int = -1) {
    if left == -1 && right == -1 {
        left = 0
        right = list.count - 1
    }

    func partition(inout list:[Int], left:Int, right:Int) -> Int {
        var i = left

        for j in left+1...right {
            if list[j] < list[left] {
                i++

                (list[i], list[j]) = (list[j], list[i])
            }
        }

        (list[i], list[left]) = (list[left], list[i])
        return i
    }

    if right > left {
        let pivotIndex = partition(&list, left, right)
        quicksort(&list, left: left, right: pivotIndex - 1)
        quicksort(&list, left: pivotIndex + 1, right: right)
    }
}