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36 lines
1.1 KiB
Python
36 lines
1.1 KiB
Python
#!/usr/bin/env python
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# coding=utf-8
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#######################################################################################
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# Bellman-Ford 单源最短路径算法
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#######################################################################################
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from typing import Dict
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def bellmanFord(distances: Dict, origin: str):
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# edges => 用来存放所有的边
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# result => 用来存放最短距离的映射结果
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edges, result = [], {}
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for node, neighbours in distances.items():
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for neighbour, weight in neighbours.items():
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edges.append((node, neighbour, weight))
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result[node] = float('inf')
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result[origin] = 0
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# 每轮都使用所有的边对节点进行松弛操作，最多运行n-1轮
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for i in range(len(distances) - 1):
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for u, v, w in edges:
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if result[v] > result[u] + w:
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result[v] = result[u] + w
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return result
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if __name__ == '__main__':
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distances = {
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'A': {'C': 4, 'B': 2},
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'B': {'A': 1, 'G': 1},
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'C': {'B': -3, 'G': 1},
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'G': {}
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}
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print(bellmanFord(distances, 'A'))
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