Submission #59637

#	Time	Username	Problem	Language	Result	Execution time	Memory
59637		IvanC	Network (BOI15_net)	C++17	100 / 100	754 ms	153032 KiB

net

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

const int MAXN = 5*1e5 + 10;

vector<int> grafo[MAXN],folhas;
int N;

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

int main(){

	scanf("%d",&N);
	for(int i = 1;i<N;i++){
		int u,v;
		scanf("%d %d",&u,&v);
		grafo[u].push_back(v);
		grafo[v].push_back(u);
	}

	dfs(1,-1);

	int ans = (folhas.size() + 1)/2;
	int delta = (folhas.size())/2;
	printf("%d\n",ans);
	for(int i = 0;i<ans;i++){
		printf("%d %d\n",folhas[i],folhas[i + delta]);
	}

	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:16:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&N);
  ~~~~~^~~~~~~~~
net.cpp:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&u,&v);
   ~~~~~^~~~~~~~~~~~~~~

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