Submission #226249

#	Time	Username	Problem	Language	Result	Execution time	Memory
226249		Fasho	Network (BOI15_net)	C++14	100 / 100	540 ms	69112 KiB

net

#include <bits/stdc++.h>
#define N 1000005
#define ll long long int 	
#define MP make_pair
#define pb push_back
#define ppb pop_back
#define sp " "
#define endl "\n"
#define fi first
#define se second
#define ii pair<int,int>
#define lli pair<ll,ll>
#define fast cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(false)
#define fast2 freopen ("badhair.gir","r",stdin);freopen ("badhair.cik","w",stdout);
#define mod 1000000007
#define fs(x,y) for(ll i=1;i<=y;i++) cin>>x[i]
#define fo(i,x,y) for(ll i=x;i<=y;i++)
#define INF 1000000000005
#define ull unsigned long long int
using namespace std;

ll n,m,ar[N],sum,t;

vector<int> v[N],ans;

void f(int ind,int back)
{
	for(int i=0;i<v[ind].size();i++)
	{
		if(v[ind][i]!=back)
			f(v[ind][i],ind);
	}

	if(v[ind].size()==1)
		ans.pb(ind);
}

int main()
{
	fast;
	cin>>n;
	int root=1;
	fo(i,1,n-1)
	{
		int a,b;
		cin>>a>>b;
		v[a].pb(b);
		v[b].pb(a);
		if(v[a].size()!=1)
			root=a;
		if(v[b].size()!=1)
			root=b;
	}
	f(root,root);
	cout<<(ans.size()+1)/2<<endl;
	for(int i=0;i<ans.size()/2;i++)
		cout<<ans[i]<<sp<<ans[i+ans.size()/2]<<endl;
	if(ans.size()%2==1)
		cout<<ans[ans.size()-1]<<sp<<ans[0]<<endl;
}

Compilation message (stderr)

net.cpp: In function 'void f(int, int)':
net.cpp:28:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v[ind].size();i++)
              ~^~~~~~~~~~~~~~
net.cpp: In function 'int main()':
net.cpp:56:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<ans.size()/2;i++)
              ~^~~~~~~~~~~~~

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