C语言qsort函数怎么用？

2015-02-09 05:26:14 1.6k 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

C语言-qsort函数详解实际上应该传p地址空间中arr1，arr2的地址，这样strcmp()才能找到arr1和arr2对应的字符串，因此得先把e1，e2转化成char**，这样解引用以后才是一个char*的地址。对于这种写法，传进去的是p的地址，strcmp()会将p地址对应的内容转化成字符串，也就是将p中arr1，arr2，arr3的地址转化成字符串。->调试后发现：e2存放的是p的地址（char**类型），e1存放的是p指向的下一个元素的地址（char**类型）比较年龄->实际比较的是整形。阅读详情



#include <iostream>

using namespace std;



typedef struct

{

    unsigned long id;

    int score;

}record;



int main()

{

    int id_cmp(const void* s1,const void* s2);

    int score_cmp(const void* s1,const void* s2);



    record recordset[] = {{3,99},{5,87},{4,56},{2,100},{1,17}};



    int recordcount = sizeof(recordset) / sizeof(record);



    printf("排序前:\n");

    for(int i = 0; i < recordcount;i++)

        printf("%8d %8u %8d\n",i,recordset[i].id,recordset[i].score);



    qsort(recordset,recordcount,sizeof(record),id_cmp);

    printf("排序后:\n");

    for(int i = 0; i < recordcount;i++)

        printf("%8d %8u %8d\n",i,recordset[i].id,recordset[i].score);





    qsort(recordset,recordcount,sizeof(record),score_cmp);

    printf("排序后:\n");

    for(int i = 0; i < recordcount;i++)

        printf("%8d %8u %8d\n",i,recordset[i].id,recordset[i].score);



    return 0;

}



int id_cmp(const void* s1,const void* s2)

{

    record* p1 = (record* )s1;

    record* p2 = (record* )s2;

    if(p1->id < p2->id) return -1;

    else if(p1->id == p2->id) return 0;

    else return 1;

}



int score_cmp(const void* s1,const void* s2)  //这个函数指针为什么能改变排序顺序

{

    record* p1 = (record* )s1;

    record* p2 = (record* )s2;

    if(p1->score < p2->score) return -1;

    else if(p1->score == p2->score) return 0;

    else return 1;

}