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Fix mypy errors at bfs_shortest_path algo (#4572)

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Hasanul Islam 2021-07-27 14:09:17 +06:00 committed by GitHub
parent 6732fa0131
commit c5003a2c46
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1 changed files with 16 additions and 12 deletions
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28
graphs/breadth_first_search_shortest_path.py
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@ -3,6 +3,8 @@ from a given source node to a target node in an unweighted graph.
"""
from __future__ import annotations
from typing import Optional
graph = {
"A": ["B", "C", "E"],
"B": ["A", "D", "E"],
@ -15,17 +17,19 @@ graph = {
class Graph:
def __init__(self, graph: dict[str, str], source_vertex: str) -> None:
"""Graph is implemented as dictionary of adjacency lists. Also,
def __init__(self, graph: dict[str, list[str]], source_vertex: str) -> None:
"""
Graph is implemented as dictionary of adjacency lists. Also,
Source vertex have to be defined upon initialization.
"""
self.graph = graph
# mapping node to its parent in resulting breadth first tree
self.parent = {}
self.parent: dict[str, Optional[str]] = {}
self.source_vertex = source_vertex
def breath_first_search(self) -> None:
"""This function is a helper for running breath first search on this graph.
"""
This function is a helper for running breath first search on this graph.
>>> g = Graph(graph, "G")
>>> g.breath_first_search()
>>> g.parent
@ -44,7 +48,8 @@ class Graph:
queue.append(adjacent_vertex)
def shortest_path(self, target_vertex: str) -> str:
"""This shortest path function returns a string, describing the result:
"""
This shortest path function returns a string, describing the result:
1.) No path is found. The string is a human readable message to indicate this.
2.) The shortest path is found. The string is in the form
`v1(->v2->v3->...->vn)`, where v1 is the source vertex and vn is the target
@ -64,17 +69,16 @@ class Graph:
'G'
"""
if target_vertex == self.source_vertex:
return f"{self.source_vertex}"
elif not self.parent.get(target_vertex):
return self.source_vertex
target_vertex_parent = self.parent.get(target_vertex)
if target_vertex_parent is None:
return f"No path from vertex:{self.source_vertex} to vertex:{target_vertex}"
else:
return self.shortest_path(self.parent[target_vertex]) + f"->{target_vertex}"
return self.shortest_path(target_vertex_parent) + f"->{target_vertex}"
if __name__ == "__main__":
import doctest
doctest.testmod()
g = Graph(graph, "G")
g.breath_first_search()
print(g.shortest_path("D"))