快速排序算法实现

#include <stdio.h>
#include <stdlib.h>

static void my_qsort(int *arr, int min, int max)
{
    int i, j, key;

    i = min;
    j = max;
    key = arr[i];

    /* 结束条件 */
    if (min > max) {
        return;
    }

    while (i < j) {
        while (i < j && arr[j] >= key) {
            j--;
        }
        arr[i] = arr[j];

        while (i < j && arr[i] <= key) {
            i++;
        }

        arr[j] = arr[i];
    }

    arr[i] = key;

    my_qsort(arr, min, i-1);
    my_qsort(arr, i+1, max);
}

int main()
{
    int *arr;
    int num, i;

    printf("enter numbers' count:\n");
    scanf("%d", &num);
    arr = (int *)malloc(num * sizeof(int));
    if (arr == NULL) {
        printf("malloc failed\n");
        return -1;
    }

    for (i = 0; i < num; i++) {
        printf("enter %d num\n", i);
        scanf("%d", &arr[i]);
    }

    printf("sort before");
    for (i = 0; i < num; i++) {
        printf("%d ", arr[i]);
    }


    my_qsort(arr, 0, num - 1);

    printf("sort after");
    for (i = 0; i < num; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
    free(arr);

    return 0;
}