Submission #330592

#	Time	Username	Problem	Language	Result	Execution time	Memory
330592		Sho10	Network (BOI15_net)	C++14	100 / 100	537 ms	52984 KiB

net

#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define all(a) (a).begin(), (a).end()
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod (10*10*10*10*10*10*10*10*10+7)
#define PI 3.14159265359
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START  ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n;
vector<ll>g[500005];
vector<ll>leaf;
void dfs(ll node,ll par){
if(g[node].size()==1){
    leaf.pb(node);
}
for(auto it : g[node]){
    if(it==par){
        continue;
    }else {
    //cnt++;
    dfs(it,node);
    }
}
}
int32_t main(){
CODE_START;
cin>>n;
for(ll i=1;i<=n-1;i++)
{
    ll x,y;
    cin>>x>>y;
    g[x].pb(y);
    g[y].pb(x);
}
ll cnt=0;
for(ll i=1;i<=n;i++)
{
    if(g[i].size()!=1){
            dfs(i,0);
            break;
    }
}
cout<<(leaf.size()+1)/2<<endl;
for(ll i=0;i<leaf.size()/2;i++)
{
    cout<<leaf[i]<<' '<<leaf[i+leaf.size()/2]<<endl;
}
if(leaf.size()%2){
    cout<<leaf[0]<<' '<<leaf.back()<<endl;
}
}

Compilation message (stderr)

net.cpp: In function 'int32_t main()':
net.cpp:56:13: 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]
   56 | for(ll i=0;i<leaf.size()/2;i++)
      |            ~^~~~~~~~~~~~~~
net.cpp:47:4: warning: unused variable 'cnt' [-Wunused-variable]
   47 | ll cnt=0;
      |    ^~~

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