Submission #824330

#	Time	Username	Problem	Language	Result	Execution time	Memory
824330		irmuun	Network (BOI15_net)	C++17	100 / 100	359 ms	70976 KiB

net

#include<bits/stdc++.h>

using namespace std;

#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    ll n;
    cin>>n;
    vector<ll>adj[n+1];
    for(ll i=1;i<n;i++){
        ll a,b;
        cin>>a>>b;
        adj[a].pb(b);
        adj[b].pb(a);
    }
    ll mx=0,ind;
    for(ll i=1;i<=n;i++){
        if(adj[i].size()>mx){
            mx=adj[i].size();
            ind=i;
        }
    }
    vector<ll>ord;
    function <void(ll,ll)> dfs=[&](ll x,ll p){
        if(adj[x].size()==1){
            ord.pb(x);
        }
        for(auto y:adj[x]){
            if(y!=p){
                dfs(y,x);
            }
        }
    };
    for(auto x:adj[ind]){
        dfs(x,ind);
    }
    if(ord.size()%2==1){
        ord.pb(ord[0]);
    }
    ll sz=ord.size();
    cout<<sz/2<<"\n";
    for(ll i=0;i<sz/2;i++){
        cout<<ord[i]<<' '<<ord[i+sz/2]<<"\n";
    }
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:25:25: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   25 |         if(adj[i].size()>mx){
      |            ~~~~~~~~~~~~~^~~
net.cpp:23:13: warning: 'ind' may be used uninitialized in this function [-Wmaybe-uninitialized]
   23 |     ll mx=0,ind;
      |             ^~~

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