fork download
copy 
  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define ll long long
  4. #define enter(v) for(int i=0;i<v.size();i++)cin>>v[i]
  5. #define leave(v) for(int i=0;i<v.size();i++){if(i)cout<<" ";cout<<v[i]}
  6.  
  7. vector<bool>visited;
  8.  
  9. void dfs2(vector<int>adj[],int u){
  10.     visited[u]=1;
  11.     for(int i=0;i<adj[u].size();i++){
  12.         int v=adj[u][i];
  13.         if(!visited[v]){
  14.             dfs2(adj,v);
  15.         }
  16.     }
  17. }
  18.  
  19. int main(){
  20.     ios::sync_with_stdio(false);
  21.     cin.tie(nullptr);
  22.  
  23.     int n,m;
  24.     cin>>n>>m;
  25.  
  26.     vector<int>adj[n+1];
  27.     for(int i=0;i<m;i++){
  28.         int f,s;
  29.         cin>>f>>s;
  30.         adj[f].push_back(s);
  31.         adj[s].push_back(f);
  32.     }
  33.  
  34.     bool can=true;
  35.  
  36.     if(n==1){
  37.         cout<<(m==0?"YES\n":"NO\n");
  38.         return 0;
  39.     }
  40.  
  41.     if(m!=n-1){
  42.         cout<<"NO\n";
  43.         return 0;
  44.     }
  45.  
  46.     visited.assign(n+1,0);
  47.     dfs2(adj,1);
  48.  
  49.     for(int i=1;i<=n;i++){
  50.         if(!visited[i]){
  51.             can=false;
  52.             break;
  53.         }
  54.     }
  55.  
  56.     cout<<(can?"YES\n":"NO\n");
  57. }
  58.  
Success #stdin #stdout 0s 5260KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
NO
https://ideone.com/vKH98k
language:
C++14 (gcc 8.3)
created:
7 hours ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!