Submission #76787

#	Time	Username	Problem	Language	Result	Execution time	Memory
76787		shoemakerjo	Network (BOI15_net)	C++14	0 / 100	13 ms	12148 KiB

net

#include <bits/stdc++.h>

using namespace std;

#define maxn 500010
int n;
vector<vector<int>> adj(maxn);

vector<int> leaves;

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

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin >> n;
	int a, b;
	for (int i = 0; i < n-1; i++) {
		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 || i == n) {
			dfs(i, -1);
			break;
		}
	}
	cout << (leaves.size()+1)/2 << endl;
	for (int i = 0; i < leaves.size()/2; i++) {
		cout << leaves[i] << " " << leaves[leaves.size()-i-1] << endl;
	}
	if (leaves.size() % 2) {
		cout << leaves[leaves.size()/2] << " " << leaves[0] << endl;
	}
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:35:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < leaves.size()/2; i++) {
                  ~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37