import Foundation

func contains(array: [Int], rand: Int) -> Bool{
    for number in array {
        if(number == rand){
            return true
        }
    }
    return false
}

func quicksort(array: [Int], lowIndex: Int, highIndex: Int){
    if(lowIndex >= highIndex){
        return;
    }

    let pivot: Int = array[highIndex]
    var leftPointer = lowIndex
    var rightPointer = highIndex

    while(leftPointer < rightPointer){
        while(array[leftPointer] <= pivot && leftPointer < rightPointer){
            leftPointer = leftPointer + 1
        }

        while(array[rightPointer] >= pivot && leftPointer < rightPointer){
            rightPointer = rightPointer - 1
        }

            array.swapAt(leftPointer, rightPointer)
    }

    if(array[leftPointer] > array[highIndex]){
        array.swapAt(leftPointer, highIndex)
    } else{
        leftPointer = highIndex
    }

    quicksort(array: array, lowIndex: lowIndex, highIndex: leftPointer - 1)
    quicksort(array: array, lowIndex: leftPointer + 1, highIndex: highIndex)
}

func quicksort(array: [Int]){
    quicksort(array: array, lowIndex: 0, highIndex: array.count - 1)
}

func main(){
    var array = [Int.random(in: 0..<30)]
    var jArray = 0

    while(jArray < 20){
        let rand = Int.random(in: 0..<21)
        if(!contains(array: array, rand: rand)){
            array.append(rand)
            jArray = jArray + 1
        }
        else{}
    }

    print("Before:")
    print(array)
    print("\nAfter:")
    quicksort(array: array)
    print(array)    
}

main()

我试图在Swift中实现类似的快速排序，swapAt方法抛出了一个错误：**错误：不能对不变的值使用突变成员：‘array’是一个‘let’常量。**我尝试了几个修复程序，但似乎都不起作用，所以我希望这里有人能帮助我，谢谢。