Submission #1032556

#	Time	Username	Problem	Language	Result	Execution time	Memory
1032556		vjudge1	Network (BOI15_net)	C++17	0 / 100	7 ms	12124 KiB

net

#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pld pair<ld, ld>
#define pb push_back
#define fi first
#define se second
#define debug(x) cout << #x << " => " << x << endl
#define all(x) x.begin(),x.end()

vector<int> adj[500010];

int main()
{
	ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
	int n;cin>>n;
	for(int i=1;i<n;i++)
	{
		int u,v;cin>>u>>v;
		adj[u].pb(v);
		adj[v].pb(u);
	}

	vector<int> v;
	for(int i=1;i<=n;i++) if(adj[i].size()==1) v.pb(i);
	vector<pii> ans;
	for(int i=0;i<v.size()-1;i+=2)
	{
		ans.pb({v[i],v[i+1]});
	}
	if(v.size()&1) for(int i=1;i<=n;i++)
	{
		if(adj[v.back()].back()!=i && i!=v.back())
		{
			ans.pb({v.back(),i});
			break;
		}
	}
	cout<<ans.size()<<'\n';
	for(auto i : ans) cout<<i.fi<<' '<<i.se<<'\n';
	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:31:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |  for(int i=0;i<v.size()-1;i+=2)
      |              ~^~~~~~~~~~~

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