数据结构上机实验之二分查找

#include <stdio.h>
#include <stdlib.h>

int Binsearch(int a[], int s, int t, int key)
{
    int low=s, high=t, mid;
    if(s<=t)
    {
        mid=low+(high-low)/2;
        if(a[mid]==key)
        {
            return mid;
        }
        if(a[mid]>key)
            return Binsearch(a,low,mid-1,key);
        else
            return Binsearch(a,mid+1,high,key);
    }
    return -1;
}

int main()
{
    int i,n,key,a[100000];
    int flag;
    while(scanf("%d",&n)!=EOF)
    {
        for(i=0; i<n; i++)
        {
            scanf("%d",&a[i]);
        }
        scanf("%d",&key);
        flag=Binsearch(a,0,n-1,key);
        if(flag==-1)
            printf("NO\n");
        else
            printf("YES\n");
    }
    return 0;
}