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  1. #include <bits/stdc++.h>
  2. #define fst ios_base::sync_with_stdio(0); ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  3. #define PI acos(-1.0)
  4. #define rd freopen("ip.txt","r",stdin)
  5. #define wr freopen("op.txt", "w", stdout)
  6. #define wis(x) cerr << #x << " is " << x << endl;
  7. #define mem(array,int) memset(array,int,sizeof(array))
  8. #define lld long long int
  9. #define nl cout<<endl;
  10. #define mx 200009
  11. #define MOD 1000000007
  12. #define pii pair<int,int>
  13. #define INF 1000009
  14. using namespace std;
  15.  
  16. //const int mx = 1e5+5;
  17.  
  18.  
  19.  
  20.  
  21. vector<int>G[mx],city;
  22.  
  23. int color[mx] ,vis[mx],par[mx],dist[mx],N,E;
  24.  
  25.  
  26.  
  27. void DFS(int n){
  28.  
  29.  
  30.     color[n] = 1;
  31.     vis[n]++;
  32.  
  33.     for (int i=0; i<G[n].size(); i++) {
  34.         int x = G[n][i];
  35.  
  36.         if (color[x] == 0) {
  37.             DFS(x);
  38.         }
  39.     }
  40.     // color[n] = 2;
  41.     //cout<<n<<" ";
  42.  
  43. }
  44.  
  45.  
  46.  
  47. int main()
  48. {
  49.  
  50.   //  rd;
  51.     //wr;
  52.     fst;
  53.  
  54.  
  55.  
  56.     while(cin>>N>>E)
  57.     {
  58.  
  59.         for(int i=0;i<E;i++)
  60.         {
  61.             int u,v;
  62.             cin >> u >> v;
  63.             G[u].push_back(v);
  64.            // G[v].push_back(u);
  65.         }
  66.  
  67.         for (int i = 1; i <= N; ++i)
  68.         {
  69.             DFS(i);
  70.             mem(color,0);
  71.            // nl;
  72.         }
  73.  
  74.        // int lim = sizeof(vis)/sizeof(*vis);
  75.         for (int i = 1; i <= N ; ++i)
  76.         {
  77.             if (vis[i] == N)
  78.             {
  79.                 city.push_back(i);
  80.             }
  81.           //  printf("%d == %d\n",i,vis[i] );
  82.         }
  83.         int lim = city.size();
  84.         //cout<<lim<<endl;
  85.  
  86.         printf("%d\n",lim );
  87.         for (int i = 0; i < lim; ++i)
  88.         {
  89.            // cout<<city[i]<<" ";
  90.             printf("%d ",city[i] );
  91.         }
  92.         nl;
  93.         mem(vis,0);
  94.         mem(color,0);
  95.         for (int i = 0; i < mx; ++i)
  96.         {
  97.             G[i].clear();
  98.         }
  99.  
  100.  
  101.     }
  102.  
  103.  
  104.     return 0;
  105. }
Success #stdin #stdout 0s 23048KB
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stdout 
Standard output is empty
https://ideone.com/7UPvAc
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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