Python/data_structures/Graph/DepthFirstSearch.py

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# Author: OMKAR PATHAK
from __future__ import print_function
class Graph():
def __init__(self):
self.vertex = {}
# for printing the Graph vertexes
def printGraph(self):
print(self.vertex)
for i in self.vertex.keys():
print(i,' -> ', ' -> '.join([str(j) for j in self.vertex[i]]))
# for adding the edge beween two vertexes
def addEdge(self, fromVertex, toVertex):
# check if vertex is already present,
if fromVertex in self.vertex.keys():
self.vertex[fromVertex].append(toVertex)
else:
# else make a new vertex
self.vertex[fromVertex] = [toVertex]
def DFS(self):
# visited array for storing already visited nodes
visited = [False] * len(self.vertex)
# call the recursive helper function
for i in range(len(self.vertex)):
if visited[i] == False:
self.DFSRec(i, visited)
def DFSRec(self, startVertex, visited):
# mark start vertex as visited
visited[startVertex] = True
print(startVertex, end = ' ')
# Recur for all the vertexes that are adjacent to this node
for i in self.vertex.keys():
if visited[i] == False:
self.DFSRec(i, visited)
if __name__ == '__main__':
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)
g.printGraph()
print('DFS:')
g.DFS()
# OUTPUT:
# 0  ->  1 -> 2
# 1  ->  2
# 2  ->  0 -> 3
# 3  ->  3
# DFS:
# 0 1 2 3