源代码: 
#include<stdio.h>
void binary_search(int key,int a[],int n)
{
	int low,high,mid,count=0,count1=0;
	low=0;
	high=n-1;
	while(low<high)
	{
		count++;
		mid=(low+high)/2;
		if(key<a[mid])
			high=mid-1;
		else if(key>a[mid])
			low=mid+1;
		else if(key==a[mid])
		{
			printf("查找成功!\n 查找 %d 次!a[%d]=%d",count,mid,key);
			count1++;
			break;
		}
	}
	if(count1==0)
		printf("查找失败!");
}
void main()
{
	int i,key,a[100],n;
	printf("请输入数组的长度：");
	scanf("%d",&n);
	printf("请输入数组元素：");
	for(i=0;i<n;i++)
		scanf("%d",&a[i]);
	printf("请输入你想要的元素：");
	scanf("%d",&key);
	binary_search(key,a,n);
	printf("\n");
}

大致的思想和思路和数据结构里面的二分法查询差不多的...