Submission #1098036

#	Time	Username	Problem	Language	Result	Execution time	Memory
1098036		AndrijaM	Network (BOI15_net)	C++14	100 / 100	430 ms	49740 KiB

net

#include <bits/stdc++.h>
using namespace std;

#define int long long

const int maxn=5e5+10;
const int mod=998244353;

vector<int>g[maxn];
vector<int>v;

void dfs(int node,int par)
{
    if(g[node].size()==1)
    {
        v.push_back(node);
        return ;
    }
    for(auto ax:g[node])
    {
        if(ax==par)continue;
        dfs(ax,node);
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ///freopen("lexicografic.in","r",stdin);
    ///freopen("lexicografic.out","w",stdout);
    int n;
    cin>>n;
    for(int i=0;i<n-1;i++)
    {
        int a,b;
        cin>>a>>b;
        a--;b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    for(int i=0;i<n;i++)
    {
        if(g[i].size()!=1)
        {
            dfs(i,-1);
            break;
        }
    }
    vector<pair<int,int>>ans;
    int kol=v.size();
    kol/=2;
    for(int i=0;i<kol;i++)
    {
        ans.push_back({v[i],v[i+kol]});
    }
    if(v.size()%2==1)
    {
        ans.push_back({v[0],v[v.size()-1]});
    }
    cout<<ans.size()<<endl;
    for(auto ax:ans)
    {
        cout<<ax.first+1<<" "<<ax.second+1<<endl;
    }
    return 0;
}

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