题解

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