qsort函数和bsearch函数的使用

1. qsort排序 

 /* qsort example */
 #include <stdio.h>
 #include <stdlib.h>

 int values[] = { 40, 10, 100, 90, 20, 25 };

 int compare (const void * a, const void * b)
 {
   return ( *(int*)a - *(int*)b );
 }

 int main ()
 {
   int n;
   qsort (values, 6, sizeof(int), compare);
   for (n=0; n<6; n++)
      printf ("%d ",values[n]);
   return 0;
 }

Output:

10 20 25 40 90 100

 

2.bsearch查找：

    
    
    
    
/* bsearch example */
#include <stdio.h>
#include <stdlib.h>

int compareints (const void * a, const void * b)
{
  return ( *(int*)a - *(int*)b );
}

int values[] = { 10, 20, 25, 40, 90, 100 };

int main ()
{
  int * pItem;
  int key = 40;
  pItem = (int*) bsearch (&key, values, 6, sizeof (int), compareints);
  if (pItem!=NULL)
    printf ("%d is in the array.\n",*pItem);
  else
    printf ("%d is not in the array.\n",key);
  return 0;
}

Output:

40 is in the array

3.两者结合用法：

 /* bsearch example with strings */
 #include <stdio.h>
 #include <stdlib.h>

 char strvalues[][20] = {"some","example","strings","here"};

 int main ()
 {
   char * pItem;
   char key[20] = "example";

   /* sort elements in array: */
   qsort (strvalues, 4, 20, (int(*)(const void*,const void*)) strcmp);

   /* search for the key: */
   pItem = (char*) bsearch (key, strvalues, 4, 20, (int(*)(const void*,const void*)) strcmp);

   if (pItem!=NULL)
     printf ("%s is in the array.\n",pItem);
   else
     printf ("%s is not in the array.\n",key);
   return 0;
 }

说明：

    
    
    
    
void qsort ( void * base, size_t num, size_t size, int ( * comparator ) ( const void *, const void * ) );
void * bsearch ( const void * key, const void * base, size_t num, size_t size, int ( * comparator ) ( const void *, const void * ) );

 
更多请参考：http://www.cplusplus.com/reference/clibrary/cstdlib/qsort/
转自：http://blog.csdn.net/dyx1024/article/details/6992703