C++ Program to Create a Random Linear Extension for a DAG

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This is a C++ Program to find random linear extension of DAG. Linear extension is another term for finding topological sort of a graph.

Here is source code of the C++ Program to Create a Random Linear Extension for a DAG. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

  1. // A C++ program to print topological sorting of a DAG
  2. #include<iostream>
  3. #include <list>
  4. #include <stack>
  5. using namespace std;
  6.  
  7. // Class to represent a graph
  8. class Graph
  9. {
  10.         int V; // No. of vertices'
  11.  
  12.         // Pointer to an array containing adjacency listsList
  13.         list<int> *adj;
  14.  
  15.         // A function used by topologicalSort
  16.         void topologicalSortUtil(int v, bool visited[], stack<int> &Stack);
  17.     public:
  18.         Graph(int V); // Constructor
  19.  
  20.         // function to add an edge to graph
  21.         void addEdge(int v, int w);
  22.  
  23.         // prints a Topological Sort of the complete graph
  24.         void topologicalSort();
  25. };
  26.  
  27. Graph::Graph(int V)
  28. {
  29.     this->V = V;
  30.     adj = new list<int> [V];
  31. }
  32.  
  33. void Graph::addEdge(int v, int w)
  34. {
  35.     adj[v].push_back(w); // Add w to v’s list.
  36. }
  37.  
  38. // A recursive function used by topologicalSort
  39. void Graph::topologicalSortUtil(int v, bool visited[], stack<int> &Stack)
  40. {
  41.     // Mark the current node as visited.
  42.     visited[v] = true;
  43.  
  44.     // Recur for all the vertices adjacent to this vertex
  45.     list<int>::iterator i;
  46.     for (i = adj[v].begin(); i != adj[v].end(); ++i)
  47.         if (!visited[*i])
  48.             topologicalSortUtil(*i, visited, Stack);
  49.  
  50.     // Push current vertex to stack which stores result
  51.     Stack.push(v);
  52. }
  53.  
  54. // The function to do Topological Sort. It uses recursive topologicalSortUtil()
  55. void Graph::topologicalSort()
  56. {
  57.     stack<int> Stack;
  58.  
  59.     // Mark all the vertices as not visited
  60.     bool *visited = new bool[V];
  61.     for (int i = 0; i < V; i++)
  62.         visited[i] = false;
  63.  
  64.     // Call the recursive helper function to store Topological Sort
  65.     // starting from all vertices one by one
  66.     for (int i = 0; i < V; i++)
  67.         if (visited[i] == false)
  68.             topologicalSortUtil(i, visited, Stack);
  69.  
  70.     // Print contents of stack
  71.     while (Stack.empty() == false)
  72.     {
  73.         cout << Stack.top() << " ";
  74.         Stack.pop();
  75.     }
  76. }
  77.  
  78. // Driver program to test above functions
  79. int main()
  80. {
  81.     // Create a graph given in the above diagram
  82.     Graph g(6);
  83.     g.addEdge(5, 2);
  84.     g.addEdge(5, 0);
  85.     g.addEdge(4, 0);
  86.     g.addEdge(4, 1);
  87.     g.addEdge(2, 3);
  88.     g.addEdge(3, 0);
  89.  
  90.     cout << "Following is a Topological Sort of the given graph \n";
  91.     g.topologicalSort();
  92.  
  93.     return 0;
  94. }

Output:

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$ g++ RandomLinearExtensionOfDAG.cpp
$ a.out
 
Following is a Topological Sort of the given graph 
5 4 2 3 1 0
------------------
(program exited with code: 0)
Press return to continue

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Here’s the list of Best Reference Books in C++ Programming, Data Structures and Algorithms.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn