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[pre-commit.ci] auto fixes from pre-commit.com hooks

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pre-commit-ci[bot] 2024-10-10 22:19:44 +00:00
parent 2b50d97d3e
commit 40e312af1b
1 changed files with 24 additions and 7 deletions
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31
graphs/bellman_ford.py
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@ -14,20 +14,29 @@ def print_distance_and_paths(distance: List[float], paths: List[List[int]], src:
print(f"{vertex}\t\t{dist}\t\t\t\t{path_str}")
def check_negative_cycle(graph: List[Edge], distance: List[float], predecessor: List[int]) -> bool:
def check_negative_cycle(
graph: List[Edge], distance: List[float], predecessor: List[int]
) -> bool:
"""
Checks if there is a negative weight cycle reachable from the source vertex.
If found, return True, indicating a negative cycle.
"""
for edge in graph:
if distance[edge.src] != float("inf") and distance[edge.src] + edge.weight < distance[edge.dst]:
if (
distance[edge.src] != float("inf")
and distance[edge.src] + edge.weight < distance[edge.dst]
):
# Update predecessors to indicate a cycle for affected paths
predecessor[edge.dst] = -1 # Use -1 as a marker for negative cycle detection
predecessor[
edge.dst
] = -1 # Use -1 as a marker for negative cycle detection
return True
return False
def reconstruct_paths(predecessor: List[int], vertex_count: int, src: int) -> List[List[int]]:
def reconstruct_paths(
predecessor: List[int], vertex_count: int, src: int
) -> List[List[int]]:
"""
Reconstructs the shortest paths from the source vertex to each vertex using the predecessor list.
"""
@ -47,7 +56,9 @@ def reconstruct_paths(predecessor: List[int], vertex_count: int, src: int) -> Li
return paths
def bellman_ford(graph: List[Edge], vertex_count: int, src: int) -> Tuple[List[float], List[List[int]]]:
def bellman_ford(
graph: List[Edge], vertex_count: int, src: int
) -> Tuple[List[float], List[List[int]]]:
"""
Returns the shortest paths from a vertex src to all other vertices, including path reconstruction.
"""
@ -58,7 +69,10 @@ def bellman_ford(graph: List[Edge], vertex_count: int, src: int) -> Tuple[List[f
# Step 1: Relax edges repeatedly
for _ in range(vertex_count - 1):
for edge in graph:
if distance[edge.src] != float("inf") and distance[edge.src] + edge.weight < distance[edge.dst]:
if (
distance[edge.src] != float("inf")
and distance[edge.src] + edge.weight < distance[edge.dst]
):
distance[edge.dst] = distance[edge.src] + edge.weight
predecessor[edge.dst] = edge.src
@ -75,6 +89,7 @@ def bellman_ford(graph: List[Edge], vertex_count: int, src: int) -> Tuple[List[f
if __name__ == "__main__":
# Example graph input for testing purposes
import doctest
doctest.testmod()
try:
@ -85,7 +100,9 @@ if __name__ == "__main__":
for i in range(E):
print(f"Edge {i + 1}")
src, dest, weight = map(int, input("Enter source, destination, weight: ").strip().split())
src, dest, weight = map(
int, input("Enter source, destination, weight: ").strip().split()
)
if src < 0 or src >= V or dest < 0 or dest >= V:
print(f"Invalid vertices: src and dest should be between 0 and {V - 1}")
continue