제출 #534483

#제출 시각아이디문제언어결과실행 시간메모리
534483Yazan_AlattarNetwork (BOI15_net)C++14
0 / 100
7 ms12044 KiB
#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef unsigned long long ull; #define F first #define S second #define pb push_back #define endl "\n" #define all(x) x.begin(), x.end() const int M = 500007; const ll inf = 1e18; const ll mod = 1e9+7; const double pi = acos(-1); const int dx[] = {0, -1, 0, 1}, dy[] = {1, 0, -1, 0}; const int block = 320; int n; vector <int> v, adj[M]; bool vist[M]; int main(){ cin >> n; for(int i = 1; i < n; ++i){ int a, b; cin >> a >> b; adj[a].pb(b); adj[b].pb(a); } for(int i = 1; i <= n; ++i) if(adj[i].size() == 1) v.pb(i); cout << ((int)v.size() + 1) / 2 << endl; for(int i = 0; i < (int)v.size() - 1; i += 2) cout << v[i] << " " << v[i + 1] << endl; if((int)v.size() % 2){ vist[v.back()] = 1; for(auto i : adj[v.back()]) vist[i] = 1; for(int i = 1; i <= n; ++i) if(!vist[i]){ cout << v.back() << " " << i << endl; break; } } return 0; }
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