请帮我用C++写一段快速排序的代码

以下是快速排序的 C 代码：

#include <stdio.h>

void quicksort(int arr[], int left, int right) {
    int i = left, j = right;
    int tmp;
    int pivot = arr[(left + right) / 2];

    /* partition */
    while (i <= j) {
        while (arr[i] < pivot)
            i++;
        while (arr[j] > pivot)
            j--;
        if (i <= j) {
            tmp = arr[i];
            arr[i] = arr[j];
            arr[j] = tmp;
            i++;
            j--;
        }
    };

    /* recursion */
    if (left < j)
        quicksort(arr, left, j);
    if (i < right)
        quicksort(arr, i, right);
}

int main() {
    int arr[] = {5, 2, 8, 3, 1, 6, 9, 7, 4};
    int n = sizeof(arr) / sizeof(arr[]);
    int i;

    printf("Before sorting:\n");
    for (i = ; i < n; i++)
        printf("%d ", arr[i]);

    quicksort(arr, , n - 1);

    printf("\nAfter sorting:\n");
    for (i = ; i < n; i++)
        printf("%d ", arr[i]);

    return ;
}