제출 #931855

#제출 시각아이디문제언어결과실행 시간메모리
931855Erfan1386YNetwork (BOI15_net)C++17
0 / 100
3 ms12124 KiB
#include <bits/stdc++.h> #define file_io freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout); #define fast_io ios::sync_with_stdio(false);cin.tie(0); #define what(x) cerr << #x << " is " << x << '\n'; #define kill(x) {cout << x << endl; return 0;} #define all(x) (x).begin(), (x).end() #define pii pair<int, int> #define pb push_back #define ll long long #define F first #define S second const ll inf = 1e18, mod = 1e9 + 7, delta = 1e9 + 9, SQ = 450, P = 6065621; using namespace std; const int N = 5e5 + 10, LG = 40; vector<int> adj[N], l; void dfs (int v, int p = -1) { if (adj[v].size() == 1) l.pb(v); for (auto u: adj[v]) if (u - p) dfs(u, v); } int main () { fast_io; int n; cin >> n; for (int i = 1; i < n; i++) { int u, v; cin >> u >> v; adj[u].pb(v); adj[v].pb(u); } dfs(1); cout << ceil(l.size() / 2) << '\n'; int t = (l.size() + 1) / 2; for (int i = 0; i < t; i++) cout << l[i] << ' ' << l[i + l.size() / 2] << '\n'; return 0; }
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