//用二分法查找数组中元素
#include<stdio.h>
#include<stdlib.h> 
#define N 15

int main()
{
	int arr[N]={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
	int low=0;       //记录下标 
	int high=N-1;
	int middle;   
	int value;       //需要查找的数 
	int flag;
	printf("输入要查找数据:");
	scanf("%d",&value); 
	if(value<arr[0]&&value>arr[N-1])
	   printf("输入的数据非法\n");
    else
       while(low<=high)
        {
        	middle=(low+high)/2;
        	if(arr[middle]<value)   //左侧数据去掉 
        		low=middle+1;
            else if(arr[middle]==value)
        		{
				   flag=middle;
				   break;
        		}
        		
        	else if(arr[middle]>value)   //右侧去掉
			    high=middle-1;
			else
				   flag=-1;
        }
    if(flag==-1)
      printf("没有找到要找的数据\n");
    else 
      printf("要找的数据是arr[%d]=%d\n",flag,arr[flag]); 
    return 0;
}