直接上代码

#include <bits/stdc++.h>
using namespace std;

int main(){
	int n,a[1100000],b,q;
    cin>>n>>q;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=q;i++){
        cin>>b;
        if(a[lower_bound(a+1,a+n+1,b)-a]==b){
            cout<<lower_bound(a+1,a+n+1,b)-a<<" ";
        }
        else{
            cout<<-1<<" ";
        }
    }
	return 0;
}