Submission #24995

#	Time	Username	Problem	Language	Result	Execution time	Memory
24995		minimario	Network (BOI15_net)	C++14	100 / 100	703 ms	42508 KiB

net

#include <bits/stdc++.h>

using namespace std;

const int MAX = 500000;
vector<int> g[MAX];
vector<int> order;

void dfs(int u, int p) {
	for (int i : g[u]) {
		if (i == p) { continue; }
		dfs(i, u);
	}
	if (g[u].size() == 1) { order.push_back(u); }
}

int main() {
	/*
	freopen("a.in", "r", stdin);
	freopen("a.out", "w", stdout);
	*/
	int n; scanf("%d", &n);
	for (int i = 0; i < n-1; ++i)
	{
		int u, v; scanf("%d %d", &u, &v);
		u--; v--;
		g[u].push_back(v);
		g[v].push_back(u);
	}
	dfs(0, -1);
	for (int i = 0; i < order.size(); ++i)
	{
		order[i]++;
	}
	printf("%d\n", ((int)order.size()+1)/2);
	for (int i = 0; i < ((int)order.size())/2; ++i) 
	{
		printf("%d %d\n", order[i], order[i+(order.size())/2]);
	}
	if (order.size() % 2 == 1) { printf("%d %d\n", order[0], order.back()); }
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:31:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < order.size(); ++i)
                    ^
net.cpp:22:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n; scanf("%d", &n);
                        ^
net.cpp:25:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int u, v; scanf("%d %d", &u, &v);
                                   ^

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