结构 - 分选C-字符串的qsort [英] struct - sorting a c-string with qsort

问题描述

我在整理一堆IP地址，但由于某种原因，他们在错误的顺序。我不太清楚的地方可能是问题。

I'm sorting a bunch of IPs, but for some reason they come in the wrong order. I'm not quite sure where could be the problem.

66.249.71.3      
190.148.164.245  
207.46.232.182   
190.148.164.245  
190.148.164.245  
202.154.114.253
190.148.164.245  
190.148.164.245  
66.249.71.3      
190.148.164.245  
202.154.114.253

这是林对它们进行排序的方式。

Here it is the way Im sorting them.

typedef struct {
    char *ip;
} mystruct;

/* qsort */
int struct_cmp(const void *a, const void *b)
{
    mystruct *ia = (mystruct *)a;
    mystruct *ib = (mystruct *)b;
    return strcmp(ia->ip, ib->ip);
} 
...
qsort(a_struct, 11, sizeof(mystruct*), struct_cmp);
for(..){
    printf("%s\n",a_struct[i]->ip);
}

任何帮助将AP preciate它。谢谢

Any help will be appreciate it. Thanks

推荐答案

您已经指针到 MYSTRUCT 数组S，但的qsort 这个比较函数期望 MYSTRUCT s的简单数组。排序 MYSTRUCT *数组你需要间接的另一个层次添加到比较功能：

You have an array of pointers to mystructs, but qsort with this comparision function would expect a simple array of mystructs. To sort an array of mystruct* you need to add another level of indirection to the comparison function:

int struct_cmp(const void *a, const void *b) {
    mystruct *ia = *(mystruct **)a;
    mystruct *ib = *(mystruct **)b;
    return strcmp(ia->ip, ib->ip);
}

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