26 lines
757 B
Perl
26 lines
757 B
Perl
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:- op(700, xfx, l).
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:- op(700, xfx, r).
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From l To :- From to To-_.
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From r To :- From to _-To.
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answer(Answer) :- starts(Starts), path([], Starts, Answer).
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path(_, EndNodes, []) :- all_ends(EndNodes), !.
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path(Directions, FromList, Moves) :-
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next_step(Directions, Move, Remain),
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maplist(Move, FromList, ToList),
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path(Remain, ToList, RemainingMoves),
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Moves is RemainingMoves + 1.
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next_step([Move | Remain], Move, Remain).
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next_step([], Move, Remain) :- direction(Str), atom_chars(Str, [Move | Remain]).
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starts(StartNodes) :-
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findall(Node, Node to _, Nodes),
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include(is_start, Nodes, StartNodes).
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all_ends(Nodes) :- maplist(is_end, Nodes).
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is_start(Node) :- atom_chars(Node, [_, _, a]).
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is_end(Node) :- atom_chars(Node, [_, _, z]).
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