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| 1 | +// A C++ program to print topological sorting of a DAG |
| 2 | +#include<bits/stdc++.h> |
| 3 | +using namespace std; |
| 4 | + |
| 5 | +// Class to represent a graph |
| 6 | +class Graph |
| 7 | +{ |
| 8 | + int V; // No. of vertices' |
| 9 | + |
| 10 | + // Pointer to an array containing adjacency listsList |
| 11 | + list<int> *adj; |
| 12 | + |
| 13 | + // A function used by topologicalSort |
| 14 | + void topologicalSortUtil(int v, bool visited[], stack<int> &Stack); |
| 15 | +public: |
| 16 | + Graph(int V); // Constructor |
| 17 | + |
| 18 | + // function to add an edge to graph |
| 19 | + void addEdge(int v, int w); |
| 20 | + |
| 21 | + // prints a Topological Sort of the complete graph |
| 22 | + void topologicalSort(); |
| 23 | +}; |
| 24 | + |
| 25 | +Graph::Graph(int V) |
| 26 | +{ |
| 27 | + this->V = V; |
| 28 | + adj = new list<int>[V]; |
| 29 | +} |
| 30 | + |
| 31 | +void Graph::addEdge(int v, int w) |
| 32 | +{ |
| 33 | + adj[v].push_back(w); // Add w to v’s list. |
| 34 | +} |
| 35 | + |
| 36 | +// A recursive function used by topologicalSort |
| 37 | +void Graph::topologicalSortUtil(int v, bool visited[], |
| 38 | + stack<int> &Stack) |
| 39 | +{ |
| 40 | + // Mark the current node as visited. |
| 41 | + visited[v] = true; |
| 42 | + |
| 43 | + // Recur for all the vertices adjacent to this vertex |
| 44 | + list<int>::iterator i; |
| 45 | + for (i = adj[v].begin(); i != adj[v].end(); ++i) |
| 46 | + if (!visited[*i]) |
| 47 | + topologicalSortUtil(*i, visited, Stack); |
| 48 | + |
| 49 | + // Push current vertex to stack which stores result |
| 50 | + Stack.push(v); |
| 51 | +} |
| 52 | + |
| 53 | +// The function to do Topological Sort. It uses recursive |
| 54 | +// 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 |
| 65 | + // Sort 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, 1); |
| 89 | + |
| 90 | + cout << "Following is a Topological Sort of the given graph \n"; |
| 91 | + g.topologicalSort(); |
| 92 | + |
| 93 | + return 0; |
| 94 | +} |
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