#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
const int MAXN = 1e9;
int n, m;
vector <int> num;

int b_s(vector<int>& tmp, int tgt){//二分 
	int l = 0;
	int r = tmp.size() - 1;
	
	int ans = -2;
	
	while(l <= r){
		int mid = l + ((r - l) >> 1);
		if(tmp[mid] == tgt) {
			ans = mid;
			r = mid - 1;
		} else if (tmp[mid] < tgt) {
			l = mid + 1;	
		}else {
			r = mid - 1;
		}
	}
	return ans;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);//提升读入速度 
	
	cin >> n >> m;
	for(int i = 0;i < n;i++) {
		int x;
		cin >> x;
		num.push_back(x);
	}
	
	while(m--){
		int op;
		cin >> op;
		int ans = b_s(num, op);
		cout << ans + 1 << ' ';//下标加1，如果找不到输出-2+1就是-1(不要学我qqq) 
	}
	return 0;
}

这题不是用来讲倍增的吗

#include<bits/stdc++.h>
using namespace std;
const int N = 1e6+10;
int n,m,a[N];
int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> n >> m;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
	}
	while(m--){
		int x,p=0,st=1;cin>>x;
		while(1){
			if(p+st<=n&&a[st-p]<x)p+=st,st<<=1;
			else st>>=1;
			if(!st){
				if(a[p+1]==x)cout<<p+1<<' ';
				else cout<<-1<<' '; 
				break;
			}
		}
		
	}
	return 0; 
}

代码有错，改一个字符。

#include<bits/stdc++.h>
using namespace std;
long long n,m,a[1000010];
int main(){
  cin>>n>>m;
  for(int i=1;i<=n;i++){
    cin>>a[i];
	}
	while(m){
		long long q;
		cin>>q;
		long long ans=lower_bound(a+1,a+1+n,q)-a;
		if(a[ans]==q)cout<<ans<<" ";
		else cout<<-1<<" ";
		m--;
	}
	return 0;
}

#include<bits/stdc++.h> using namespace std; long long n,m,a[1000010]; int main(){ cin>>n>>m; for(int i=1;i<=n;i++){ cin>>a[i]; } while(m){ long long q; cin>>q; long long ans=lower_bound(a+1,a+1+n,q)-a; if(a[ans]==q)cout<<ans<<" "; else cout<<-1<<" "; m--; } return 0; }**

#include<bits/stdc++.h> using namespace std; long long n,m,a[1000010]; int main(){ cin>>n>>m; for(int i=1;i<=n;i++){ cin>>a[i]; } while(m){ long long q; cin>>q; long long ans=lower_bound(a+1,a+1+n,q)-a; if(a[ans]==q)cout<<ans<<" "; else cout<<-1<<" "; m--; } return 0; }