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C语言中qsort函数的应用

By Wu Yudong on June 26, 2015

原创文章,转载请注明: 转载自工学1号馆

qsort函数包含在<stdlib.h>的头文件里,本文中排序都是采用的从小到大排序

一、对int类型数组排序

int num[100]; 
int cmp ( const void *a , const void *b ) 
{ 
    return *(int *)a  - *(int *)b; 
} 
qsort(num,100,sizeof(num[0]),cmp);

二、对char类型数组排序(同int类型)

char word[100]; 
int cmp( const void *a , const void *b ) 
{ 
    return *(char *)a - *(char *)b; 
} 
qsort(word,100,sizeof(word[0]),cmp);

三、对double类型数组排序(特别要注意)

double in[100]; 
int cmp( const void *a , const void *b ) 
{ 
    return *(double *)a > *(double *)b ? 1 : -1; 
} 
qsort(in,100,sizeof(in[0]),cmp);

四、对结构体一级排序

struct In 
{ 
    double data; 
     int other; 
}s[100];

int cmp( const void *a ,const void *b) 
{ 
    return (*(struct In *)a)->data > (*(struct In *)b)->data ? 1 : -1; 
} 
qsort(s,100,sizeof(s[0]),cmp);

 五、对结构体二级排序

struct In 
{ 
   int x; 
   int y; 
}s[100]; 

//按照x从小到大排序,当x相等时按照y从大到小排序 
int cmp( const void *a , const void *b ) 
{ 
    struct In *c = (struct In *)a; 
    struct In *d = (struct In *)b; 
    if(c->x != d->x) return c->x - d->x; 
    else return d->y - c->y; 
} 
qsort(s,100,sizeof(s[0]),cmp);

 六、对字符串进行排序

struct In 
{ 
    int data; 
    char str[100]; 
}s[100]; 

//按照结构体中字符串str的字典顺序排序 
int cmp ( const void *a , const void *b ) 
{ 
    return strcmp( (*(struct In *)a)->str , (*(struct In *)b)->str ); 
} 
qsort(s,100,sizeof(s[0]),cmp);

 

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