二分查找模板

#include<bits/stdc++.h>
using namespace std:
int a[105];
int n,x;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++）{
		cin>>a[i];
	}
	cin>>x;
	int l=1,r=n;
	int ans = -1;
	while(l<=r){
		int mid = (l+r)/2:
		if(a[mid]==x){
			ans = mid;
			break;
		}else if(a[mid]>x){
			r = mid -1;
		}else if(a[mid]<x){
			l = mid + 1;
		}
	}
	cout<<ans;
	return 0;
}