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Copy pathbreadth_first_search.py
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90 lines (74 loc) · 2.29 KB
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#!/usr/bin/python
""" Author: OMKAR PATHAK """
from __future__ import annotations
class Graph:
def __init__(self) -> None:
self.vertices: dict[int, list[int]] = {}
def print_graph(self) -> None:
"""
prints adjacency list representation of graaph
>>> g = Graph()
>>> g.print_graph()
>>> g.add_edge(0, 1)
>>> g.print_graph()
0 : 1
"""
for i in self.vertices:
print(i, " : ", " -> ".join([str(j) for j in self.vertices[i]]))
def add_edge(self, from_vertex: int, to_vertex: int) -> None:
"""
adding the edge between two vertices
>>> g = Graph()
>>> g.print_graph()
>>> g.add_edge(0, 1)
>>> g.print_graph()
0 : 1
"""
if from_vertex in self.vertices:
self.vertices[from_vertex].append(to_vertex)
else:
self.vertices[from_vertex] = [to_vertex]
def bfs(self, start_vertex: int) -> set[int]:
"""
>>> g = Graph()
>>> g.add_edge(0, 1)
>>> g.add_edge(0, 1)
>>> g.add_edge(0, 2)
>>> g.add_edge(1, 2)
>>> g.add_edge(2, 0)
>>> g.add_edge(2, 3)
>>> g.add_edge(3, 3)
>>> sorted(g.bfs(2))
[0, 1, 2, 3]
"""
# initialize set for storing already visited vertices
visited = set()
# create a first in first out queue to store all the vertices for BFS
queue = []
# mark the source node as visited and enqueue it
visited.add(start_vertex)
queue.append(start_vertex)
while queue:
vertex = queue.pop(0)
# loop through all adjacent vertex and enqueue it if not yet visited
for adjacent_vertex in self.vertices[vertex]:
if adjacent_vertex not in visited:
queue.append(adjacent_vertex)
visited.add(adjacent_vertex)
return visited
if __name__ == "__main__":
from doctest import testmod
testmod(verbose=True)
g = Graph()
g.add_edge(0, 1)
g.add_edge(0, 2)
g.add_edge(1, 2)
g.add_edge(2, 0)
g.add_edge(2, 3)
g.add_edge(3, 3)
g.print_graph()
# 0 : 1 -> 2
# 1 : 2
# 2 : 0 -> 3
# 3 : 3
assert sorted(g.bfs(2)) == [0, 1, 2, 3]