Submission #1207432

#	Time	Username	Problem	Language	Result	Execution time	Memory
1207432		rhm_gan	Network (BOI15_net)	C++20	100 / 100	446 ms	46232 KiB

net

#include <bits/stdc++.h>
using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 42
#endif

#define int long long

const int N = 5e5 + 1;
vector<int> adj[N];
vector<int> v;

void dfs(int u, int p) {
	if (adj[u].size() == 1) {
		v.push_back(u);
	}
	for (auto v : adj[u]) {
		if (v != p) dfs(v, u);
	}
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    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);
    }

    dfs(1, 0);

   	int m = v.size();
   	cout << (m + 1) / 2 << '\n';
   	for (int i = 0; i < m / 2; i++) {
   		cout << v[i] << ' ' << v[i + m / 2] << '\n';
   	}
   	if (m & 1) {
   		cout << v.back() << ' ' << v[0] << '\n'; 
   	}

    return 0;
}

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