제출 #1175991

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1175991		belgianbot	Network (BOI15_net)	C++20	0 / 100	0 ms	324 KiB

net

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

vector<vector<int>> adj, divi;
int n;
void dfs(int x, int pre, int dv) {
    for (int y : adj[x]) {
        if (pre == y) continue;
        dfs(y, x, dv);
    }
    if (adj[x].size() == 1) divi[dv].push_back(x);
}
signed main() {
    cin >> n;
    adj.resize(n);

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

    int root = -1;
    for (int i = 0; i < n; i++) if (adj[i].size() > 1) root = i;
    divi.resize(adj[root].size());

    for (int i = 0; i < adj[root].size(); i++)dfs(adj[root][i], root, i);


    vector<pair<int,int>> res;
    for (int i = 0; i < divi.size(); i++) {
        if (i == divi.size() - 1) {
            for (int j = 0; j < divi[i].size(); j++) res.push_back({divi[i][j], root});
        }
        for (int j = 0; j < divi[i].size(); j++) {
            res.push_back({divi[i][j], divi.back().back()});
            divi.back().pop_back();
            if (divi.back().empty()) {
                divi.pop_back();
                if (i == divi.size() - 1) {
                    while (++j < divi[i].size()) {
                        res.push_back({divi[i][j], root});
                    }
                }
            }
        }
    }

    cout << res.size() << '\n';
    for (auto x : res) cout << x.first+1 << ' ' << x.second+1 << '\n';



}

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