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Handled type annotations and added doctests

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This commit is contained in:
Joelkurien 2024-10-28 13:28:21 +11:00
parent 9a4e1d333f
commit af534ade82
1 changed files with 20 additions and 2 deletions
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22
graphs/johnson_graph.py
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@ -7,20 +7,32 @@ import sys
# https://brilliant.org/wiki/johnsons-algorithm/ # https://brilliant.org/wiki/johnsons-algorithm/
class JohnsonGraph: class JohnsonGraph:
def __init__(self) -> None: def __init__(self) -> None:
self.edges: list[str] = [] """
self.graph: dict[str, list] = {} Initializes an empty graph with no edges.
"""
self.edges: list[tuple[str, str, int]] = []
self.graph: dict[str, list[tuple[str, int]]] = {}
# add vertices for a graph # add vertices for a graph
def add_vertices(self, u:int) -> None: def add_vertices(self, u:int) -> None:
"""
Adds a vertex `u` to the graph with an empty adjacency list.
"""
self.graph[u] = [] self.graph[u] = []
# assign weights for each edges formed of the directed graph # assign weights for each edges formed of the directed graph
def add_edge(self, u:str, v:str, w:int) -> None: def add_edge(self, u:str, v:str, w:int) -> None:
"""
Adds a directed edge from vertex `u` to vertex `v` with weight `w`.
"""
self.edges.append((u, v, w)) self.edges.append((u, v, w))
self.graph[u].append((v, w)) self.graph[u].append((v, w))
# perform a dijkstra algorithm on a directed graph # perform a dijkstra algorithm on a directed graph
def dijkstra(self, s:str) -> dict: def dijkstra(self, s:str) -> dict:
"""
Computes the shortest path from vertex `s` to all other vertices using Dijkstra's algorithm.
"""
distances = {vertex: sys.maxsize - 1 for vertex in self.graph} distances = {vertex: sys.maxsize - 1 for vertex in self.graph}
pq = [(0, s)] pq = [(0, s)]
distances[s] = 0 distances[s] = 0
@ -38,6 +50,9 @@ class JohnsonGraph:
# carry out the bellman ford algorithm for a node and estimate its distance vector # carry out the bellman ford algorithm for a node and estimate its distance vector
def bellman_ford(self, s:str) -> dict: def bellman_ford(self, s:str) -> dict:
"""
Computes the shortest path from vertex `s` to all other vertices using the Bellman-Ford algorithm.
"""
distances = {vertex: sys.maxsize - 1 for vertex in self.graph} distances = {vertex: sys.maxsize - 1 for vertex in self.graph}
distances[s] = 0 distances[s] = 0
@ -52,6 +67,9 @@ class JohnsonGraph:
# could not be handled by either the dijkstra # could not be handled by either the dijkstra
# or the bellman ford algorithm efficiently # or the bellman ford algorithm efficiently
def johnson_algo(self) -> list[dict]: def johnson_algo(self) -> list[dict]:
"""
Computes the shortest paths between all pairs of vertices using Johnson's algorithm.
"""
self.add_vertices("#") self.add_vertices("#")
for v in self.graph: for v in self.graph:
if v != "#": if v != "#":