二分法搜索bsearch使用举例

#include <stdlib.h>

#include <stdio.h>

 

#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))

 

int numarray[] = {123, 145, 512, 627, 800, 933};

 

int numeric (const int *p1, const int *p2)

{

   return(*p1 - *p2);

}

 

int lookup(int key)

{

   int *itemptr;

 

   /* The cast of (int(*)(const void *,const void*))

      is needed to avoid a type mismatch error at

      compile time */

   itemptr = bsearch (&key, numarray, NELEMS(numarray),

      sizeof(int), (int(*)(const void *,const void *))numeric);

 

   return (itemptr != NULL);

}

 

int main(void)

{

   if (lookup(512))

      printf("512 is in the table./n");

   else

      printf("512 isn't in the table./n");

 

   return 0;

}