lower_bound简单解决

#include<bits/stdc++.h>
using namespace std;
int main(){
int n, m;
cin >> n >> m;
int a[n+3];
for(int i=1; i<=n; i++)cin >> a[i];
while(m--){
int t;
cin >> t;
int x = lower_bound(a+1, a+n+1, t)-a;
if(a[x]!=t)cout << -1;
else cout <<x;
cout << " ";
}
}