手写快速排序

 public static void quicksort(int arr[], int left, int right){

        int index;
        if (left < right) {
            index = partition(arr, left, right);
            quicksort(arr, left, index - 1);
            quicksort(arr, index + 1, right);
        }
    }

    public static int partition(int arr[], int left, int right){
        int key = arr[left];
        while (left < right){
            while (right > left&& arr[right]>= key)
                right --;
            if (right > left)
                arr[left++] = arr[right];
            while (left < right && arr[left] <= key)
                left++;
            if (left < right)
                arr[right--] = arr[left];
        }
        arr[left] = key;
        return left;
    }