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* Update queue implementation Popping the first element of a list takes O(n) time. Using a cyclic queue takes O(1) time. * Add queue changes from extra files * Update indentation * Add empty line between imports * Fix lines * Apply suggestions from code review Co-authored-by: John Law <johnlaw.po@gmail.com> Co-authored-by: John Law <johnlaw.po@gmail.com>
93 lines
2.3 KiB
Python
93 lines
2.3 KiB
Python
#!/usr/bin/python
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""" Author: OMKAR PATHAK """
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from __future__ import annotations
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from queue import Queue
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class Graph:
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def __init__(self) -> None:
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self.vertices: dict[int, list[int]] = {}
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def print_graph(self) -> None:
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"""
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prints adjacency list representation of graaph
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>>> g = Graph()
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>>> g.print_graph()
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>>> g.add_edge(0, 1)
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>>> g.print_graph()
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0 : 1
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"""
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for i in self.vertices:
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print(i, " : ", " -> ".join([str(j) for j in self.vertices[i]]))
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def add_edge(self, from_vertex: int, to_vertex: int) -> None:
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"""
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adding the edge between two vertices
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>>> g = Graph()
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>>> g.print_graph()
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>>> g.add_edge(0, 1)
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>>> g.print_graph()
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0 : 1
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"""
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if from_vertex in self.vertices:
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self.vertices[from_vertex].append(to_vertex)
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else:
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self.vertices[from_vertex] = [to_vertex]
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def bfs(self, start_vertex: int) -> set[int]:
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"""
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>>> g = Graph()
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>>> g.add_edge(0, 1)
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>>> g.add_edge(0, 1)
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>>> g.add_edge(0, 2)
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>>> g.add_edge(1, 2)
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>>> g.add_edge(2, 0)
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>>> g.add_edge(2, 3)
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>>> g.add_edge(3, 3)
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>>> sorted(g.bfs(2))
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[0, 1, 2, 3]
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"""
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# initialize set for storing already visited vertices
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visited = set()
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# create a first in first out queue to store all the vertices for BFS
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queue = Queue()
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# mark the source node as visited and enqueue it
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visited.add(start_vertex)
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queue.put(start_vertex)
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while not queue.empty():
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vertex = queue.get()
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# loop through all adjacent vertex and enqueue it if not yet visited
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for adjacent_vertex in self.vertices[vertex]:
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if adjacent_vertex not in visited:
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queue.put(adjacent_vertex)
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visited.add(adjacent_vertex)
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return visited
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if __name__ == "__main__":
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from doctest import testmod
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testmod(verbose=True)
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g = Graph()
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g.add_edge(0, 1)
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g.add_edge(0, 2)
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g.add_edge(1, 2)
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g.add_edge(2, 0)
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g.add_edge(2, 3)
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g.add_edge(3, 3)
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g.print_graph()
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# 0 : 1 -> 2
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# 1 : 2
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# 2 : 0 -> 3
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# 3 : 3
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assert sorted(g.bfs(2)) == [0, 1, 2, 3]
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