DFS.py

# Python program to print DFS traversal for complete 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[v]= True
        print v,

        # Recur for all the vertices adjacent to
        # this vertex
        for i in self.graph[v]:
            if visited[i] == False:
                self.DFSUtil(i, visited)


    # The function to do DFS traversal. It uses
    # recursive DFSUtil()
    def DFS(self):
        V = len(self.graph)  #total vertices

        # Mark all the vertices as not visited
        visited =[False]*(V)

        # Call the recursive helper function to print
        # DFS traversal starting from all vertices one
        # by one
        for i in range(V):
            if visited[i] == False:
                self.DFSUtil(i, 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 Depth First Traversal"
g.DFS()