제출 #932994

#제출 시각아이디문제언어결과실행 시간메모리
932994ArashJafariyanNetwork (BOI15_net)C++17
100 / 100
340 ms38504 KiB
#include <bits/stdc++.h> #ifdef DEBUG #include "debug.h" #else #define debug(...) 0 #endif typedef long long ll; #pragma GCC optimize("O3,unroll-loops") #pragma GCC target("avx2") int main() { std::ios::sync_with_stdio(0); std::cin.tie(0); int n; std::cin >> n; std::vector<std::vector<int>> adj(n); for (int i = 1; i < n; i++) { int v, u; std::cin >> v >> u; v--; u--; adj[v].push_back(u); adj[u].push_back(v); } std::vector<int> leaf; auto dfs = [&](auto self, int v, int p) -> void { if (adj[v].size() == 1) { leaf.push_back(v); } for (int u : adj[v]) { if (u != p) { self(self, u, v); } } }; dfs(dfs, 0, 0); int sz = leaf.size(); std::cout << (sz + 1) / 2 << '\n'; for (int i = 0; i + sz / 2 < sz; i++) { std::cout << leaf[i] + 1 << ' ' << leaf[i + sz / 2] + 1 << '\n'; } return 0; }
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