Merge pull request #19 from SundaramDubey/patch-1

Added topological Sort

Algorithms/Sorting/topologicalSort.cpp

@@ -0,0 +1,97 @@
+// A C++ program to print topological sorting of a DAG 
+#include<iostream> 
+#include <list> 
+#include <stack> 
+using namespace std; 
+
+// Class to represent a graph 
+class Graph 
+{ 
+	int V; // No. of vertices' 
+
+	// 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: 
+	Graph(int V); // Constructor 
+
+	// 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) 
+{ 
+	adj[v].push_back(w); // Add w to v’s list. 
+} 
+
+// 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 program to test above functions 
+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"; 
+	g.topologicalSort(); 
+
+	return 0; 
+} 
+//contributed by Sundaram Dubey