代码

#include<iostream>
#include<cstdio>
using namespace std;

int binary_search(const unsigned *a, int n, unsigned x)
{
	register int l=0,r=n-1;
	register int ret=0,mid;
	while(l<=r) {
		mid=(l+r)>>1;
		if(a[mid]==x) return mid;
		if(a[mid]<x) l=mid+1; else r=mid-1;
	}
}

int main() {
	unsigned a[100],n,x;
	cin>>n>>x;
	for(int i=0;i<n;i++) cin>>a[i];
	cout<<binary_search(a,n,x)<<endl;
	return 0;
}

评测结果