快速排序不是一个稳定的排序

#include <stdio.h>#define N 10typedef struct Node Node;struct Node{  int num;  int id;};Node node[N];int cmp_int(const void *_p, const void *_q);int main(){  int i;  int a[N] = {1, 2, 3, 4, 5, 4, 6, 4, 7, 4};  for (i = 0; i < N; i++)  {    node[i].num = a[i];    node[i].id = i;  }  qsort(node, N, sizeof(Node), cmp_int);  for (i = 0; i < N; i++)    printf("id=%d, num=%d\n", node[i].id, node[i].num);}int cmp_int(const void *_p, const void *_q){  Node *p = (Node *)_p;  Node *q = (Node *)_q;  return p->num - q->num;}