Merge pull request div-bargali#272 from siddhamsj/patch-2

 Topological sorting.cpp

Author: jai2dev

C++/Algorithms/Sorting-Algorithms/Topological sorting.cpp

@@ -0,0 +1,109 @@
+// A C++ program to print topological 
+// output 5 4 2 3 1 0 
+// sorting of a DAG 
+#include <iostream> 
+#include <list> 
+#include <stack> 
+using namespace std; 
+
+// Class to represent a graph 
+class Graph { 
+// No. of vertices' 
+int V; 
+
+// Pointer to an array containing adjacency listsList 
+list<int>* adj; 
+
+// A function used by topologicalSort 
+void topologicalSortUtil(int v, bool visited[], 
+stack<int>& Stack); 
+
+public: 
+// Constructor 
+Graph(int V); 
+
+// function to add an edge to graph 
+void addEdge(int v, int w); 
+
+// prints a Topological Sort of 
+// the complete graph 
+void topologicalSort(); 
+}; 
+
+Graph::Graph(int V) 
+{ 
+this->V = V; 
+adj = new list<int>[V]; 
+} 
+
+void Graph::addEdge(int v, int w) 
+{ 
+// Add w to v’s list. 
+adj[v].push_back(w); 
+} 
+
+// A recursive function used by topologicalSort 
+void Graph::topologicalSortUtil(int v, bool visited[], 
+stack<int>& Stack) 
+{ 
+// Mark the current node as visited. 
+visited[v] = true; 
+
+// Recur for all the vertices 
+// adjacent to this vertex 
+list<int>::iterator i; 
+for (i = adj[v].begin(); i != adj[v].end(); ++i) 
+if (!visited[*i]) 
+topologicalSortUtil(*i, visited, Stack); 
+
+// Push current vertex to stack 
+// which stores result 
+Stack.push(v); 
+} 
+
+// The function to do Topological Sort. 
+// It uses recursive topologicalSortUtil() 
+void Graph::topologicalSort() 
+{ 
+stack<int> Stack; 
+
+// Mark all the vertices as not visited 
+bool* visited = new bool[V]; 
+for (int i = 0; i < V; i++) 
+visited[i] = false; 
+
+// Call the recursive helper function 
+// to store Topological 
+// Sort starting from all 
+// vertices one by one 
+for (int i = 0; i < V; i++) 
+if (visited[i] == false) 
+topologicalSortUtil(i, visited, Stack); 
+
+// Print contents of stack 
+while (Stack.empty() == false) { 
+cout << Stack.top() << " "; 
+Stack.pop(); 
+} 
+} 
+
+// Driver Code 
+int main() 
+{ 
+// Create a graph given in the above diagram 
+Graph g(6); 
+g.addEdge(5, 2); 
+g.addEdge(5, 0); 
+g.addEdge(4, 0); 
+g.addEdge(4, 1); 
+g.addEdge(2, 3); 
+g.addEdge(3, 1); 
+
+cout << "Following is a Topological Sort of the given "
+"graph \n"; 
+
+// Function Call 
+g.topologicalSort(); 
+
+return 0; 
+}