Submission #1189072

#TimeUsernameProblemLanguageResultExecution timeMemory
1189072rendelNetwork (BOI15_net)C++20
0 / 100
5 ms12100 KiB
#include<bits/stdc++.h> using namespace std; const int maxn = 5e5+5; int deg[maxn]; vector<int> adj[maxn]; vector<int> g; void dfs(int u,int p){ if(deg[u]==1) g.emplace_back(u); for(auto v : adj[u]){ if(v==p) continue; dfs(v,u); } } int main(){ cin.tie(nullptr)->sync_with_stdio(false); cout.tie(0); int n; cin >> n; for(int i=0;i<n-1;++i){ int a,b; cin >> a >> b; adj[a].emplace_back(b); adj[b].emplace_back(a); deg[a]++, deg[b]++; } dfs(1,0); int l=g.size(); cout << (l+1)/2 << '\n'; for(int i=0;i<l/2;++i){ cout << g[i] << ' ' << g[l-i-1] <<'\n'; } if(l%2==1) cout << g[0] << ' ' << g[l/2] ; }
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