源码如下：
#include<stdio.h>
#include<stdlib.h>

#define MAX_LENGTH  100

typedef int KeyType;

typedef struct
{
    int key;
}ElemType;
 
typedef struct
{
    ElemType elem[MAX_LENGTH];     
    int length;
}SSTable;


int Search_Bin(SSTable ST,KeyType key)
{   
    int low,high,mid;
    low = 1;high = ST.length;
      while(low <=high)
     {
          mid = (low+high)/2;
          if(key ==ST.elem[mid].key)
              return mid;
          else
              if(key<ST.elem[mid].key)
                  high = mid-1;
              else
                  low=mid+1;
      }
      return 0;
}

void main()
{
    int i,result;
    SSTable ST;
    KeyType key;
    printf("please input length:");
    scanf("%d",&ST.length);
    for(i=1;i<=ST.length;i++)
    {
        printf("please input ST.elem:");
        scanf("%d",&ST.elem[i]);
    }
    printf("please input keyword:");
    scanf("%d",&key);
    result=Search_Bin(ST,key);
    if(result==0)
        printf("Don't find\n");
    else
        printf("Find the key,the position is %d\n",result);
}

折半查找的前提是集合已排序。