제출 #900115

#제출 시각아이디문제언어결과실행 시간메모리
900115LCJLYNetwork (BOI15_net)C++14
100 / 100
345 ms48592 KiB
#include <bits/stdc++.h> using namespace std; #define int long long #define ld long double #define show(x,y) cout << y << " " << #x << endl; #define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl; #define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl; #define show4(x,y) for(auto it:x) cout << it << " "; cout << #y << endl; typedef pair<long long,long long>pii; typedef pair<pii,pii>pi2; vector<int>adj[500005]; vector<int>leaf; void dfs(int index, int par){ if(adj[index].size()==1)leaf.push_back(index); for(auto it:adj[index]){ if(it==par) continue; dfs(it,index); } } void solve(){ int n; cin >> n; int temp,temp2; for(int x=0;x<n-1;x++){ cin >> temp >> temp2; adj[temp].push_back(temp2); adj[temp2].push_back(temp); } for(int x=1;x<=n;x++){ if(adj[x].size()>1){ dfs(x,-1); break; } } int sz=leaf.size(); cout << (sz+1)/2 << "\n"; for(int x=sz/2;x<sz;x++){ cout << leaf[x] << " " << leaf[x-sz/2] << "\n"; } cout << "\n"; } int32_t main(){ ios::sync_with_stdio(0); cin.tie(0); int t=1; //cin >> t; while(t--){ solve(); } }
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