Submission #939078

#	Time	Username	Problem	Language	Result	Execution time	Memory
939078		ezzzay	Network (BOI15_net)	C++14	100 / 100	650 ms	58084 KiB

net

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ff first
#define ss second
#define pb push_back
const int N=5e5+5;
bool vis[N];
vector<int>v[N];
vector<pair<int,int>>rts;
vector<int>vec;
void dfs(int a, int p=-1){
    if(v[a].size()==1)vec.pb(a);
    for(auto b:v[a]){
        if(b!=p){
            dfs(b,a);
        }
    }
}
signed main(){
    int n;
    cin>>n;
    for(int i=1;i<n;i++){
        int a,b;
        cin>>a>>b;
        v[a].pb(b);
        v[b].pb(a);
        rts.pb({a,b});
    }
    dfs(1);
    
    
    cout<<vec.size()/2+vec.size()%2<<endl;
    for(int i=0;i<(vec.size()+1)/2;i++){
        cout<<vec[i]<<" "<<vec[i+vec.size()/2]<<endl;
    }
    
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:34:18: 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]
   34 |     for(int i=0;i<(vec.size()+1)/2;i++){
      |                 ~^~~~~~~~~~~~~~~~~

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