Submission #51138

#	Time	Username	Problem	Language	Result	Execution time	Memory
51138		faustaadp	Network (BOI15_net)	C++17	0 / 100	12 ms	12264 KiB

net

#include<bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
ll n,ta,tb,i,dg[505050],Vs,R;
vector<ll> v[505050],V;
void dfs(ll aa,ll bb)
{
	//cout<<aa<<" "<<bb
	if(dg[aa]==1)
		V.pb(aa);
	ll ii;
	for(ii=0;ii<v[aa].size();ii++)
		if(v[aa][ii]!=bb)
			dfs(v[aa][ii],aa);
}
int main()
{
	cin>>n;
	for(i=1;i<n;i++)
	{
		cin>>ta>>tb;
		v[ta].pb(tb);
		v[tb].pb(ta);
		dg[ta]++;
		dg[tb]++;
	}
	for(i=1;i<=n;i++)
		if(dg[i]>1)
			R=i;
	dfs(R,-1);
	Vs=V.size();
	if(Vs%2==1)
	{
		V.pb(V[Vs-1]);
		Vs++;
	}
	cout<<Vs/2<<"\n";
	for(i=0;i<Vs/2;i++)
		cout<<V[i]<<" "<<V[Vs-i-1]<<"\n";
}

Compilation message (stderr)

net.cpp: In function 'void dfs(long long int, long long int)':
net.cpp:16:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(ii=0;ii<v[aa].size();ii++)
           ~~^~~~~~~~~~~~~

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