快速排序

#include <cstdio>
#include <cstdlib>
#include <ctime>

int main() {
    void QuickSort(int *a, int p, int r);
    const int MAXLEN = 10;
    int a[MAXLEN] = {3, 8, 9, 1, 0, 2, 5, 7, 4, 6};

    printf("befor sort:");
    for(int i=0; i<MAXLEN; ++i) {
        printf("%d ", a[i]);
    }
    putchar('\n');

    QuickSort(a, 0, MAXLEN-1);

    printf("after sort:");
    for(int i=0; i<MAXLEN; ++i) {
        printf("%d ", a[i]);
    }
    putchar('\n');

    return 0;
}

void Swap(int *e1, int *e2) {
    int tmp;
    tmp=*e1, *e1=*e2, *e2=tmp;
}

void QuickSort(int *a, int p, int r) {
    if (p>=r) return;

    srand(time(nullptr));
    Swap(&a[rand() % (r+1-p) + p], &a[r]);

    int key = a[r];
    int k = p;
    for (int i=p; i<r; ++i) {
        if (a[i] < a[r]) {
            Swap(&a[i], &a[k]);
            ++k;
        }
    }
    Swap(&a[k], &a[r]);

    QuickSort(a, p, k-1);
    QuickSort(a, k+1, r);
}