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  1. #include <iostream>
  2. #include <vector>
  3. #include <stack>
  4.  
  5. int n;
  6.  
  7. using namespace std;
  8. vector <int> graph[1000006];
  9. int components[1000006];
  10. int no_of_components;
  11. stack <int> mystack;
  12.  
  13. int main(){
  14.  
  15.     // Load the graph
  16.  
  17.     cin >> n;
  18.     for (int i=0; i<n; i++){
  19.         int X;
  20.         cin >> X;
  21.         graph[X-1].push_back(i); 
  22.     }
  23.  
  24.     // Display loaded graph 
  25.     cout<<"Graph:"<<endl; 
  26.     for (int i=0; i<n; i++) {
  27.     	cout << "Node "<<i<<" --> ";
  28.     	for (auto &x : graph[i]) 
  29.     	    cout<< x<< " ";
  30.     	cout<<endl;     
  31.     }  
  32.     cout<<endl; 
  33.  
  34.     // Identify the connectect groups 
  35.  
  36.     for (int i=0; i<n; i++){
  37.  
  38.         if (components[i]>0) 
  39.             continue;
  40.  
  41.         no_of_components++;
  42.  
  43.         mystack.push(i);
  44.         components[i]=no_of_components;
  45.  
  46.         while (mystack.empty()==false){
  47.             int v;
  48.  
  49.             v=mystack.top();
  50.             mystack.pop();
  51.  
  52.             for (int u=0; u<graph[v].size(); u++){
  53.                 if (components[graph[v][u]]>0) continue;
  54.  
  55.                 mystack.push(graph[v][u]);
  56.                 components[graph[v][u]]=no_of_components;
  57.  
  58.             }
  59.         }
  60.     }
  61.  
  62.     // Display resutls
  63.  
  64.     cout << "Number of connected components: "<<no_of_components<<endl;
  65.     for (int i=0;i<n; i++) 
  66.        cout <<"Node "<< i<<" is in component "<<components[i]<<endl;
  67.  
  68.     return 0;
  69.  
  70. }
Success #stdin #stdout 0s 19048KB
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stdin
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4 2 1 2 4
stdout
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Graph:
Node 0 --> 1 
Node 1 --> 0 2 
Node 2 --> 
Node 3 --> 3 

Number of connected components: 2
Node 0 is in component 1
Node 1 is in component 1
Node 2 is in component 1
Node 3 is in component 2
https://ideone.com/cAZKKP
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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