67 lines
1.4 KiB
Python
67 lines
1.4 KiB
Python
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#!/usr/bin/env python
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class Infinity:
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def __eq__(self,other):
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return isinstance(other,Infinity)
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def __gt__(self,other):
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return not isinstance(other, Infinity)
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def __lt__(self,other):
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return False
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def __add__(self,other):
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return self
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def __radd__(self,other):
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return self
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def __repr__(self):
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return "inf"
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class Graph:
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def __init__(self):
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self.nodes = set()
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self.edges = set()
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def add_node(self,node):
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self.nodes.add(node)
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def add_edge(self,nodefrom, nodeto, extra=None):
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self.edges.add( (nodefrom,nodeto,extra) )
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def all_edges_of(self,nodefrom):
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return filter(lambda e: e[0] == nodefrom, self.edges)
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def dijkstra(graph,startnode):
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d = { node: Infinity() for node in graph.nodes }
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d[startnode] = 0
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V = [startnode]
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while len(V) > 0:
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node = min(V, key=lambda e: d[e])
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V.remove(node)
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for _, neighbor, distance in graph.all_edges_of(node):
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if d[neighbor] > d[node] + distance:
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d[neighbor] = d[node] + distance
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V.append(neighbor)
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return d
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def main():
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g = Graph()
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for i in range(1,7):
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g.add_node(i)
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g.add_edge(1,2,10)
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g.add_edge(1,4,30)
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g.add_edge(1,5,100)
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g.add_edge(2,3,50)
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g.add_edge(3,5,10)
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g.add_edge(4,3,20)
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g.add_edge(4,5,60)
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d = dijkstra(g,1)
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print(d)
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if __name__ == '__main__':
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main()
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