Submission #100581

#TimeUsernameProblemLanguageResultExecution timeMemory
100581MohamedAhmed0Network (BOI15_net)C++14
0 / 100
12 ms12160 KiB
#include <bits/stdc++.h> using namespace std; const int MAX = 500005 ; int n ; vector< vector<int> >adj(MAX) ; stack<int>s ; vector<int>v ; void dfs(int node , int par) { for(auto &child : adj[node]) { if(child == par) continue; dfs(child , node) ; } if(adj[node].size() == 1) v.push_back(node) ; } int main() { scanf("%d" , &n) ; for(int i = 0 ; i < n-1 ; ++i) { int x , y ; scanf("%d %d" , &x , &y) ; adj[x].push_back(y) ; adj[y].push_back(x) ; } int leaves = 0 ; for(int i = 1 ; i <= n ; ++i) { if(adj[i].size() == 1) leaves++; } int start = -1 ; for(int i = 1 ; i <= n ; ++i) { if(adj[i].size() > 1) { start = i ; dfs(start , -1) ; break; } } int edges = (leaves + 1) / 2 ; cout<<edges<<"\n"; if(edges & 1) { cout<<v.back()<<" "<<start<<"\n"; edges-- ; v.pop_back(); } for(int i = 0 ; i < v.size()/2 ; ++i) cout<<v[i]<<" "<<v[i+edges]<<"\n"; return 0 ; }

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:59:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0 ; i < v.size()/2 ; ++i)
                     ~~^~~~~~~~~~~~
net.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d" , &n) ;
     ~~~~~^~~~~~~~~~~
net.cpp:31:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d" , &x , &y) ;
         ~~~~~^~~~~~~~~~~~~~~~~~~
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