Added solution

Author: avidLearnerInProgress

topological_sort_using_dfs.py

@@ -0,0 +1,40 @@
+
+class Graph:
+    def __init__(self, v): 
+        self.V = v
+        self.graph = [[] for _ in range(self.V)]
+        self.visited = [False] * (self.V)
+
+    def addEdge(self, u, v):
+        self.graph[u].append(v)
+
+    def helper(self, i, visited, stack):
+        '''
+        Ensure that all the adjacent nodes are explored and pushed in stack first before the parent node..
+        '''
+
+        self.visited[i] = True
+        for adjacent in self.graph[i]:
+            if not self.visited[adjacent]:
+                self.helper(adjacent, self.visited, stack)
+        stack.append(i)
+
+    def topologicalSort(self):
+        stack = []        
+        for i in range(self.V):
+            if not self.visited[i]:
+                self.helper(i, self.visited, stack)
+        print(stack[::-1])
+
+if __name__ == '__main__':
+    g = Graph(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)
+    g.topologicalSort()
+
+
+