Submission #583412

#	Time	Username	Problem	Language	Result	Execution time	Memory
583412		TheLimePixel	Network (BOI15_net)	C++17	0 / 100	1 ms	320 KiB

net

#include "bits/stdc++.h"

using namespace std;

vector<vector<int>> graph;
vector<int> leaves;
int leaf_count, res_count;

void add_leaves(int node, int parent) {
    if (graph[node].size() == 1)
        leaves.push_back(node);

    for (auto adj : graph[node])
        if (adj != parent)
            add_leaves(adj, node);
}

void run() {
    int n;
    cin >> n;

    if (n == 1) {
        cout << 0;
        return;
    }

    if (n == 2) {
        cout << "1\n2";
        return;
    }

    graph = vector<vector<int>>(n + 1);

    for (int i = 0; i < n - 1; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    for (int i = 1; i <= n; i++)
        if (graph[i].size() == 1)
            leaf_count++;

    res_count = (leaf_count + 1) / 2;
    cout << res_count;
    leaves.reserve(2 * res_count);

    add_leaves(1, 0);

    if (res_count & 1)
        leaves.push_back(leaves.front());

    for (int i = 0; i < res_count; i++)
        cout << '\n' << leaves[i] << ' ' << leaves[res_count + i];
}

auto main() -> int {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    run();
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37