#### Depth First Search 2

p
```#!/usr/bin/python

"""Author: OMKAR PATHAK"""

class Graph:
def __init__(self):
self.vertex = {}

# for printing the Graph vertices
def print_graph(self) -> None:
"""
Print the graph vertices.

Example:
>>> g = Graph()
>>> g.print_graph()
{0: [1, 2], 1: [2], 2: [0, 3], 3: [3]}
0  ->  1 -> 2
1  ->  2
2  ->  0 -> 3
3  ->  3
"""
print(self.vertex)
for i in self.vertex:
print(i, " -> ", " -> ".join([str(j) for j in self.vertex[i]]))

# for adding the edge between two vertices
def add_edge(self, from_vertex: int, to_vertex: int) -> None:
"""
Add an edge between two vertices.

:param from_vertex: The source vertex.
:param to_vertex: The destination vertex.

Example:
>>> g = Graph()
>>> g.print_graph()
{0: [1, 2]}
0  ->  1 -> 2
"""
# check if vertex is already present,
if from_vertex in self.vertex:
self.vertex[from_vertex].append(to_vertex)
else:
# else make a new vertex
self.vertex[from_vertex] = [to_vertex]

def dfs(self) -> None:
"""
Perform depth-first search (DFS) traversal on the graph
and print the visited vertices.

Example:
>>> g = Graph()
>>> g.dfs()
0 1 2 3
"""
# 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 not visited[i]:
self.dfs_recursive(i, visited)

def dfs_recursive(self, start_vertex: int, visited: list) -> None:
"""
Perform a recursive depth-first search (DFS) traversal on the graph.

:param start_vertex: The starting vertex for the traversal.
:param visited: A list to track visited vertices.

Example:
>>> g = Graph()
>>> visited = [False] * len(g.vertex)
>>> g.dfs_recursive(0, visited)
0 1 2 3
"""
# mark start vertex as visited
visited[start_vertex] = True

print(start_vertex, end="")

# Recur for all the vertices that are adjacent to this node
for i in self.vertex:
if not visited[i]:
print(" ", end="")
self.dfs_recursive(i, visited)

if __name__ == "__main__":
import doctest

doctest.testmod()

g = Graph()