int num[100]; 

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

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

qsort(word,100,sizeof(word[0]),cmp); 

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);

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); 

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); 

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);