Submission #1037003

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037003		___	Network (BOI15_net)	C++17	100 / 100	498 ms	48588 KiB

net

#include <bits/stdc++.h>
#define int long long int
#define ff first
#define ss second
#define FT ios_base::sync_with_stdio(false);cin.tie(0);
using namespace std;
const int maxn = 5e5 + 10;
vector <int> adj[maxn];
vector <int> leaf;
void dfs (int v , int g)
{
	if (adj[v].size() == 1)
	{
		leaf.push_back(v);
	}
	for (auto u : adj[v])
	{
		if (u != g)
		{
			dfs (u , v);
		}
	}
}
signed main()
{
	FT;
	int n;
	cin >> n;
	for (int i = 1 ; i < n ; i++)
	{
		int a , b;
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	for (int i = 1 ; i <= n ; i++)
	{
		if (adj[i].size() > 1)
		{
			dfs (i , 0);
			break;
		}
	}
	int k = leaf.size();
	cout << (k + 1) / 2 << endl;
	for (int i = 0 ; i < (k + 1) / 2 ; i++)
	{
		cout << leaf[i] << " " << leaf[i + k / 2] << endl;
	}
	return 0;	
}
		

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