Submission #476078

#	Time	Username	Problem	Language	Result	Execution time	Memory
476078		ZaZo_	Network (BOI15_net)	C++14	0 / 100	1 ms	1484 KiB

net

#include <bits/stdc++.h>
#define HID ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define int long long
#define all(v) v.begin(),v.end()
const int N = 50005 , INF = 1e15 , MOD=1000000006;
using namespace std;
int n ;
vector<int>edges[N];
vector<int>leaves;
int vis[N]={0};
void dfs(int node)
{
  if(edges[node].size()==1) leaves.push_back(node);
  vis[node]=1;
  for(auto x : edges[node])
    if(!vis[x])
      dfs(x);
}
int32_t main() {
  HID
  cin>>n;
  for(int i = 0 ; i < n-1 ; i++)
  {
    int u , v;
    cin >> u >> v;
    edges[u].push_back(v);
    edges[v].push_back(u);
  }
  dfs(1);
  cout<<(leaves.size()+1)/2<<endl;
  if(leaves.size()%2==0)
  {
    for(int i = 0 ; i < leaves.size() ; i+=2)
    {
      cout<<leaves[i]<<" "<<leaves[i+1]<<endl;
    }
  }
  else
  {
    for(int i = 0 ; i < leaves.size() ; i+=2)
    {
      if(i==leaves.size()-1)  break;
      cout<<leaves[i]<<" "<<leaves[i+1]<<endl;
    }
    cout<<leaves.back()<<" ";
    for(int i = 1 ; i <= n ; i++)
    {
      if(i!=leaves.back()&&i!=edges[leaves.back()][0])
      {
        cout<<i<<endl;
      }
      break;
    }
  }
}

Compilation message (stderr)

net.cpp: In function 'int32_t main()':
net.cpp:33:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |     for(int i = 0 ; i < leaves.size() ; i+=2)
      |                     ~~^~~~~~~~~~~~~~~
net.cpp:40:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     for(int i = 0 ; i < leaves.size() ; i+=2)
      |                     ~~^~~~~~~~~~~~~~~
net.cpp:42:11: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |       if(i==leaves.size()-1)  break;
      |          ~^~~~~~~~~~~~~~~~~

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