Submission #476092

#	Time	Username	Problem	Language	Result	Execution time	Memory
476092		ZaZo_	Network (BOI15_net)	C++14	63 / 100	3 ms	2764 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;
void dfs(int node , int par)
{
  if(edges[node].size()==1) leaves.push_back(node);
  for(auto x : edges[node])
    if(x!=par)
      dfs(x,node);
}
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,-1);
  cout<<(leaves.size()+1)/2<<endl;
  if(leaves.size()%2==0)
  {
    for(int i = 0 ; i < leaves.size()/2 ; i++)
    cout<<leaves[i]<<" "<<leaves[leaves.size()/2+i]<<endl;
  }
  else
  {
    for(int i = 0 ; i < leaves.size()/2 ; i++)
    {
      if(i==leaves.size()-1)  break;
      cout<<leaves[i]<<" "<<leaves[leaves.size()/2+i]<<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:31:23: 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]
   31 |     for(int i = 0 ; i < leaves.size()/2 ; i++)
      |                     ~~^~~~~~~~~~~~~~~~~
net.cpp:36:23: 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]
   36 |     for(int i = 0 ; i < leaves.size()/2 ; i++)
      |                     ~~^~~~~~~~~~~~~~~~~
net.cpp:38:11: 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]
   38 |       if(i==leaves.size()-1)  break;
      |          ~^~~~~~~~~~~~~~~~~

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