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Trip Planning

Plan a trip on the London Underground.

    
Wolfram Language code: g = \!\(\*GraphicsBox[«6»]\);
Find a shortest route from "Arsenal" to "Alperton" on the London Underground:
Wolfram Language code: station = FindShortestPath[g, "Arsenal", "Alperton"]
Construct a graph containing line information between stations:
Wolfram Language code: Clear[stop];lines = SplitBy[DeleteDuplicates[Flatten[Outer[stop, List @@ #, AnnotationValue[{g, #}, "Lines"]] & /@ EdgeList[PathGraph[station]]]], First]; stop[s_, l_] := StringJoin[{"take ", l, " at ", s}];
Wolfram Language code: linegraph = Graph[Flatten[{Outer[UndirectedEdge, {"Arsenal"}, lines[[1]]], UndirectedEdge@@@Subsets[#, {2}]& /@ lines, Outer[UndirectedEdge, #1, #2]&@@@Partition[lines, 2, 1], Outer[UndirectedEdge, lines[[-1]], {"Alperton"}]}]]
Find a shortest path that also tells a subway line at the transition:
Wolfram Language code: FindShortestPath[linegraph, "Arsenal", "Alperton"]//Column