Submission #239825

#	Time	Username	Problem	Language	Result	Execution time	Memory
239825		kshitij_sodani	Network (BOI15_net)	C++17	0 / 100	12 ms	12032 KiB

net

#include <bits/stdc++.h>
using namespace std;
typedef int64_t llo;
#define mp make_pair
#define pb push_back
#define a first 
#define b second



int n;
vector<int> adj[500001];
vector<int> kk;
void dfs(int no,int par=-1){

	for(auto j:adj[no]){
		if(j!=par){
			dfs(j,no);
		}
	}
	if(adj[no].size()==1){
		kk.pb(no);
	}
}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin>>n;
	for(int i=0;i<n-1;i++){
		int aa,bb;
		cin>>aa>>bb;
		adj[aa-1].pb(bb-1);
		adj[bb-1].pb(aa-1);

	}
	int r=0;
	for(int i=0;i<n;i++){
		if(adj[i].size()>1){
			r=i;
		}
	}
	dfs(r);
	cout<<((kk.size()+1)/2)<<endl;
	for(int i=0;i<kk.size()/2;i++){
		cout<<kk[i]+1<<" "<<kk[kk.size()-i-1]+1<<endl;
	}
	if(kk.size()%2==1){
		cout<<kk[kk.size()/2]+1<<" "<<r<<endl;
	}


	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:44:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<kk.size()/2;i++){
              ~^~~~~~~~~~~~

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