added traversal optimisation for the graph module being used

bit_manipulation/dfs.py

@@ -0,0 +1,60 @@
+# Python3 program to print DFS traversal
+# from a given given graph
+from collections import defaultdict
+
+# This class represents a directed graph using
+# adjacency list representation
+
+
+class Graph:
+
+	# Constructor
+	def __init__(self):
+
+		# default dictionary to store graph
+		self.graph = defaultdict(list)
+
+	# function to add an edge to graph
+	def addEdge(self, u, v):
+		self.graph[u].append(v)
+
+	# A function used by DFS
+	def DFSUtil(self, v, visited):
+
+		# Mark the current node as visited
+		# and print it
+		visited.add(v)
+		print(v, end=' ')
+
+		# Recur for all the vertices
+		# adjacent to this vertex
+		for neighbour in self.graph[v]:
+			if neighbour not in visited:
+				self.DFSUtil(neighbour, visited)
+
+	# The function to do DFS traversal. It uses
+	# recursive DFSUtil()
+	def DFS(self, v):
+
+		# Create a set to store visited vertices
+		visited = set()
+
+		# Call the recursive helper function
+		# to print DFS traversal
+		self.DFSUtil(v, visited)
+
+# Driver code
+
+
+# Create a graph given
+# in the above diagram
+g = Graph()
+g.addEdge(0, 1)
+g.addEdge(0, 2)
+g.addEdge(1, 2)
+g.addEdge(2, 0)
+g.addEdge(2, 3)
+g.addEdge(3, 3)
+
+print("Following is DFS from (starting from vertex 2)")
+g.DFS(2)