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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4. vector<vector<int> > g;
  5. bool vis[1000000];
  6. void dfs(int u){
  7.    vis[u]=true;
  8.    for(int i=0;i<g[u].size();++i){
  9.        int aux=g[u][i];
  10.        if(vis[aux]==false){
  11.            dfs(aux);
  12.        }
  13.    }
  14. }
  15. int main()
  16. {
  17.     int n; cin>> n;
  18.     for(int i=0;i<n;++i){
  19.         int nodos,aristas,x,y;
  20.         cin>> nodos >> aristas;
  21.         g.assign(nodos+5, vector<int> ());
  22.         memset(vis,false,sizeof vis);
  23.         for(int k=0;k<aristas;++k){
  24.             cin>> x >> y;
  25.             x--; y--;
  26.             g[x].push_back(y);
  27.             g[y].push_back(x);
  28.         }
  29.         dfs(0);
  30.         bool ok=false;
  31.         for(int i=0;i<nodos;++i){
  32.             if(vis[i]==false){
  33.                 ok=true;
  34.             }
  35.         }
  36.         if(ok==true)cout<<"NO"<<endl;
  37.         else cout<<"YES"<<endl;
  38.     }
  39.     return 0;
  40. }
  41.  
Success #stdin #stdout 0s 16216KB
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https://ideone.com/gZoXvV
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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