Submission #580242

#	Time	Username	Problem	Language	Result	Execution time	Memory
580242		Omar_Elgedawy	Network (BOI15_net)	C++14	100 / 100	658 ms	53888 KiB

net

#include <bits/stdc++.h>
using namespace std;
#define cin(vec)        for(auto& i : vec) cin >> i
#define cout(vec)       for(auto& i : vec) cout << i << " "; cout << "\n";
#define fast            ios::sync_with_stdio(0);cin.tie(0);
#define loop(i,a,b)     for (int i = a; i < b; i++)
#define F               first
#define S               second
#define pb(n)           push_back(n)
#define pf(n)           push_front(n)
#define dci(d)          fixed<<setprecision(d)
#define sp              ' '
#define el              '\n'
#define all(v)          v.begin(),v.end()
#define int             long long
int dx[8]= {0,0,1,-1,-1,1,1,-1};
int dy[8]= {-1,1,0,0,-1,1,-1,1};
int const N=5e5+5,M=1e3+1,Mod=1e9+7;
vector<int>adj[N],par[N];
vector<int>leaf;
int n;
void dfs(int u,int p){
  if(adj[u].size()==1)leaf.push_back(u);
  for(auto v:adj[u]){
    if(v!=p)dfs(v,u);
  }
}
void testcase(int h){
  cin>>n;
  for(int i=0;i<n-1;i++){
    int u,v;cin>>u>>v;
    adj[u].pb(v);
    adj[v].pb(u);
  }
  dfs(1,-1);
  // cout(leaf);
  int sz=leaf.size();
  if(sz%2){
    cout<<sz/2+1<<el;
    for(int i=0;i<sz/2;i++){
      cout<<leaf[i]<<' '<<leaf[i+sz/2+1]<<el;
    }
    cout<<leaf[sz/2]<<' '<<1<<el;
  }
  else{
    cout<<sz/2<<el;
    for(int i=0;i<sz/2;i++){
      cout<<leaf[i]<<' '<<leaf[i+sz/2]<<el;
    }
  }
}
int32_t main()
{
  // fast
  testcase(1);
  // int tc;cin>>tc;for(int i=1;i<=tc;i++)testcase(i);
  return 0;
}

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