Submission #545616

#	Time	Username	Problem	Language	Result	Execution time	Memory
545616		AbdelmagedNour	Network (BOI15_net)	C++17	100 / 100	446 ms	47688 KiB

net

#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
vector<vector<int>>adj;
vector<int>V;
void dfs(int v,int p){
    if(adj[v].size()==1)V.push_back(v);
    for(auto&u:adj[v]){
        if(u==p)continue;
        dfs(u,v);
    }
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin>>n;
    adj.resize(n);
    for(int i=1;i<n;i++){
        int u,v;
        cin>>u>>v;u--;v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    dfs(0,-1);
    int sz=V.size();
    cout<<(sz+1)/2<<"\n";
    for(int i=0;i<sz/2;i++)cout<<V[i]+1<<" "<<V[i+(sz+1)/2]+1<<"\n";
    if(sz&1)cout<<V[sz/2]+1<<" 1";
    return 0;
}

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