제출 #394759

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
394759		Saynaa	Network (BOI15_net)	C++14	100 / 100	496 ms	41040 KiB

net

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 5e5 + 10;
int n;
vector< int > adj[MAXN], ls;

void dfs(int u, int p = -1){
	if( adj[u].size() == 1) ls.push_back(u);
	for(int i = 0; i < adj[u].size(); i ++){
		int v = adj[u][i];
		if( v == p) continue;
		dfs(v, u);
	}
}

int main(){
	ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> n;
	for(int i = 1; i < n; i ++){
		int u, v;
		cin >> u >> v, u --, v --;
		adj[u].push_back(v), adj[v].push_back(u);
	}
	dfs(0);
	cout << (ls.size() + 1)/2 << '\n';
//	int pt = 0;
	for(int i = 0; i + ls.size()/2 < ls.size(); i ++){
		cout << ls[i] + 1 << " " << ls[i + ls.size()/2] + 1 << '\n';
		//pt = i;
	}
	//if( ls.size() % 2)
	return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

net.cpp: In function 'void dfs(int, int)':
net.cpp:10:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  for(int i = 0; i < adj[u].size(); i ++){
      |                 ~~^~~~~~~~~~~~~~~

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37