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[pre-commit.ci] auto fixes from pre-commit.com hooks
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@ -17,16 +17,18 @@ def print_distance_and_paths(distance: list[float], paths: list[list[int]], src:
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print(f"{vertex}\t\t{dist}\t\t\t\t{path_str}")
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def check_negative_cycle(graph: list[Edge], distance: list[float],
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predecessor: list[int]) -> bool:
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def check_negative_cycle(
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graph: list[Edge], distance: list[float], predecessor: list[int]
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) -> bool:
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"""
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Checks if there is a negative weight cycle reachable from the source vertex.
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If found, return True, indicating a negative cycle.
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"""
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for edge in graph:
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if (distance[edge.src] != float("inf") and
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distance[edge.src] + edge.weight
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< distance[edge.dst]):
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if (
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distance[edge.src] != float("inf")
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and distance[edge.src] + edge.weight < distance[edge.dst]
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):
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# Update predecessors to indicate a cycle for affected paths
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# Use -1 as a marker for negative cycle detection
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predecessor[edge.dst] = -1
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@ -34,8 +36,9 @@ predecessor: list[int]) -> bool:
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return False
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def reconstruct_paths(predecessor: list[int],
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vertex_count: int, src: int) -> list[list[int]]:
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def reconstruct_paths(
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predecessor: list[int], vertex_count: int, src: int
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) -> list[list[int]]:
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"""
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Reconstructs the shortest paths from the source vertex to
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each vertex using the predecessor list.
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@ -56,8 +59,9 @@ vertex_count: int, src: int) -> list[list[int]]:
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return paths
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def bellman_ford(graph: list[Edge],
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vertex_count: int, src: int) -> tuple[list[float], list[list[int]]]:
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def bellman_ford(
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graph: list[Edge], vertex_count: int, src: int
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) -> tuple[list[float], list[list[int]]]:
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"""
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Returns the shortest paths from a vertex src to all other vertices,
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including path reconstruction.
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@ -69,8 +73,10 @@ vertex_count: int, src: int) -> tuple[list[float], list[list[int]]]:
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# Step 1: Relax edges repeatedly
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for _ in range(vertex_count - 1):
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for edge in graph:
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if (distance[edge.src] != float("inf") and
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distance[edge.src] + edge.weight < distance[edge.dst]):
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if (
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distance[edge.src] != float("inf")
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and distance[edge.src] + edge.weight < distance[edge.dst]
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):
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distance[edge.dst] = distance[edge.src] + edge.weight
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predecessor[edge.dst] = edge.src
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@ -97,8 +103,9 @@ if __name__ == "__main__":
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for i in range(E):
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print(f"Edge {i + 1}")
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src, dest, weight = map(int,
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input("Enter source, destination, weight: ").strip().split())
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src, dest, weight = map(
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int, input("Enter source, destination, weight: ").strip().split()
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)
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if src < 0 or src >= V or dest < 0 or dest >= V:
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print(f"Invalid vertices: src and dest should be between 0 and {V - 1}")
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continue
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