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* from __future__ import annotations
* fixup! from __future__ import annotations
* fixup! from __future__ import annotations
* fixup! Format Python code with psf/black push
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
57 lines
1.6 KiB
Python
57 lines
1.6 KiB
Python
from __future__ import annotations
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def printDist(dist, V):
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print("Vertex Distance")
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distances = ("INF" if d == float("inf") else d for d in dist)
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print("\t".join(f"{i}\t{d}" for i, d in enumerate(distances)))
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def BellmanFord(graph: list[dict[str, int]], V: int, E: int, src: int) -> int:
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"""
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Returns shortest paths from a vertex src to all
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other vertices.
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"""
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mdist = [float("inf") for i in range(V)]
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mdist[src] = 0.0
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for i in range(V - 1):
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for j in range(E):
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u = graph[j]["src"]
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v = graph[j]["dst"]
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w = graph[j]["weight"]
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if mdist[u] != float("inf") and mdist[u] + w < mdist[v]:
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mdist[v] = mdist[u] + w
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for j in range(E):
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u = graph[j]["src"]
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v = graph[j]["dst"]
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w = graph[j]["weight"]
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if mdist[u] != float("inf") and mdist[u] + w < mdist[v]:
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print("Negative cycle found. Solution not possible.")
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return
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printDist(mdist, V)
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return src
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if __name__ == "__main__":
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V = int(input("Enter number of vertices: ").strip())
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E = int(input("Enter number of edges: ").strip())
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graph = [dict() for j in range(E)]
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for i in range(E):
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graph[i][i] = 0.0
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for i in range(E):
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print("\nEdge ", i + 1)
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src = int(input("Enter source:").strip())
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dst = int(input("Enter destination:").strip())
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weight = float(input("Enter weight:").strip())
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graph[i] = {"src": src, "dst": dst, "weight": weight}
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gsrc = int(input("\nEnter shortest path source:").strip())
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BellmanFord(graph, V, E, gsrc)
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