题解 | #查找#

#include<bits/stdc++.h>
#include <algorithm>
#include <iostream>
using namespace std;
int main(){
	set<int>s;

	int n,m;
	int num;
	cin>>n>>m;
	for(int i=0;i<n;i++)
	{
		cin>>num;
		s.insert(num);
	}
	
	while(m)
	{
		m--;
		cin>>num;
		int size =s.size();
		s.insert(num);
		auto it = s.find(num);
		++it;
		if(it != s.end())
		{
			cout<<*it<<endl;
		}
		else 
		{
			cout<<-1<<endl;
		}
		if(s.size() > size)
		{
			s.erase(num);
		}
		
	}


	return 0;
}