使用cin，cout优化时，该先写freopen

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int main()
{
	freopen("xxx.in","r",stdin);
	freopen("xxx.out","w",stdout);
	std::ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	
	return 0;
}

还是先写优化

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int main()
{
	std::ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	freopen("xxx.in","r",stdin);
	freopen("xxx.out","w",stdout);
	
	return 0;
}