函数指针的使用（字符串排序）

函数指针的使用（字符串排序）

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

//申请内存空间
char **apply(int len);

//返回一个字符串
char *assign();

//初始化字符串数组
void init(char **beg, char **end, char* (*operate)());

//打印字符串数组
void print(char **arr, int len);

//升序排序
int asc(const void *left, const void *right);
//将序排序
int desc(const void *left, const void *right);

int main()
{
    char **str;
    int num;//字符串个数
    srand(time(NULL));
    num = rand() % 10 + 1;
    str = apply(num);

    init(str,str+num-1,&assign);
    printf("排序前：
");
    print(str,num);

    //运用函数库的快速排序
    qsort(str,num,sizeof(char*),&asc);

    printf("排序后:
");
    print(str,num);
    return 0;
}

char **apply(int len)
{
    char **arr = (char**)calloc(len,sizeof(char*));
    return arr;
}
//返回一个字符串
char *assign()
{
    int i;
    int len = rand() % 10 + 1;//字符串长度
    char *pstr = (char*)calloc(len,sizeof(char));

    for(i = 0; i < len; i++)
        pstr[i] = rand() % 26 + 'a';
    pstr[i] = '';
    return pstr;
}

void init(char **beg, char **end, char* (*operate)())
{
    while(beg <= end)
    {
        *beg = (*operate)();
        beg++;
    }
}

void print(char **arr, int len)
{
    int i;
    for(i = 0;i < len; i++)
        printf("[%d]:%s
",i,arr[i]);
    printf("
");
}

int asc(const void *left, const void *right)
{
    char **pleft = (char**)left;
    char **pright = (char**)right;

    if(strcmp(*pleft,*pright) > 0)
        return 1;
    return 0;
}

int desc(const void *left, const void *right)
{
    char **pleft = (char**)left;
    char **pright = (char**)right;

    if(strcmp(*pleft,*pright) < 0)
        return 1;
    return 0;
}

运行结果：