Submission #910034

#	Time	Username	Problem	Language	Result	Execution time	Memory
910034		Petrix	Network (BOI15_net)	C++17	100 / 100	641 ms	61324 KiB

net

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define int long long

vector<vector<int>> v;
int frunza[500001],p[500001];
vector<pair<int,int>> rasp;
int cnt;

void dfs(int parinte,int nod){
    p[nod]=cnt;cnt++;
    int aux=0,i;
    for(i=0;i<v[nod].size();i++){
        if(v[nod][i]!=parinte){
            dfs(nod,v[nod][i]);
            aux++;
        }
    }
    if(!aux) frunza[nod]=1;
}

signed main()
{
    int n,i,a,b;cnt=0;
    cin>>n;v.resize(n+1);
    for(i=0;i<n-1;i++){
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(-1,1);
    for(i=1;i<=n;i++){
        if((i==1 && v[1].size()==1) || frunza[i])
            rasp.push_back({p[i],i});
    }
    cout<<(1ll*rasp.size()+1)/2<<"\n";
    sort(rasp.begin(),rasp.end());
    for(i=0;i<(1ll*rasp.size()+1ll)/2ll;i++){
        cout<<rasp[i].second<<" "<<rasp[i+(rasp.size()/2)].second<<"\n";
    }
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'void dfs(long long int, long long int)':
net.cpp:16:14: 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]
   16 |     for(i=0;i<v[nod].size();i++){
      |             ~^~~~~~~~~~~~~~
net.cpp: In function 'int main()':
net.cpp:41:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'long long unsigned int' [-Wsign-compare]
   41 |     for(i=0;i<(1ll*rasp.size()+1ll)/2ll;i++){
      |             ~^~~~~~~~~~~~~~~~~~~~~~~~~~

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