Submission #492423

#	Time	Username	Problem	Language	Result	Execution time	Memory
492423		Rainbowbunny	Network (BOI15_net)	C++17	100 / 100	411 ms	51892 KiB

net

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

const int MAXN = 5e5 + 5;

int n;
vector <int> Leaves;
vector <int> Adj[MAXN];

void DFS(int node, int p = -1)
{
    for(auto x : Adj[node])
    {
        if(x == p)
        {
            continue;
        }
        DFS(x, node);
    }
    if(Adj[node].size() == 1)
    {
        Leaves.push_back(node);
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n;
    for(int i = 1; i < n; i++)
    {
        int u, v;
        cin >> u >> v;
        Adj[u].push_back(v);
        Adj[v].push_back(u);
    }
    DFS(1);
    int s = Leaves.size();
    cout << (int)(s + 1) / 2 << '\n';
    for(int i = 0; i < (s + 1) / 2; i++)
    {
        cout << Leaves[i] << ' ' << Leaves[(i + (s + 1) / 2) % s] << '\n';
    }
}

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