71 lines
2.2 KiB
Prolog
71 lines
2.2 KiB
Prolog
:- use_module(library(pio)).
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:- initialization(main, main).
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main([FileName|_]) :-
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input(FileName, Map),
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propagate(Map, [0-0-3], FinalMap),
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count(FinalMap, Answer),
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write(Answer), nl.
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count(Map, X) :-
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findall(1, (nth0(_, Map, Row), nth0(_, Row, _-D), \+ D = [0,0,0,0]), Ls),
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length(Ls, X).
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% propagate(Map, Queue, NewMap). 'Dir' is 0/1/2/3 == light coming from N/E/S/W.
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propagate(Map, [], Map).
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propagate(Map, [X-Y-Dir|Queue], FinalMap) :-
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( (nth0(X, Map, Row), nth0(Y, Row, Cell-Done), nth0(Dir, Done, 0))
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-> replace(Dir, Done, 1, NewDone),
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replace(Y, Row, Cell-NewDone, NewRow),
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replace(X, Map, NewRow, NewMap),
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call(Cell, X, Y, Dir, NewCells),
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append(Queue, NewCells, NewQueue)
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; NewQueue = Queue,
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NewMap = Map
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),
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propagate(NewMap, NewQueue, FinalMap).
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'.'(X, Y, 0, [NewX-Y-0]) :- NewX is X + 1.
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'.'(X, Y, 1, [X-NewY-1]) :- NewY is Y - 1.
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'.'(X, Y, 2, [NewX-Y-2]) :- NewX is X - 1.
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'.'(X, Y, 3, [X-NewY-3]) :- NewY is Y + 1.
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'/'(X, Y, 0, [X-NewY-1]) :- NewY is Y - 1.
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'/'(X, Y, 1, [NewX-Y-0]) :- NewX is X + 1.
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'/'(X, Y, 2, [X-NewY-3]) :- NewY is Y + 1.
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'/'(X, Y, 3, [NewX-Y-2]) :- NewX is X - 1.
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'\\'(X, Y, 0, [X-NewY-3]) :- NewY is Y + 1.
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'\\'(X, Y, 1, [NewX-Y-2]) :- NewX is X - 1.
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'\\'(X, Y, 2, [X-NewY-1]) :- NewY is Y - 1.
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'\\'(X, Y, 3, [NewX-Y-0]) :- NewX is X + 1.
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'|'(X, Y, 0, NewCells) :- '.'(X, Y, 0, NewCells).
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'|'(X, Y, 2, NewCells) :- '.'(X, Y, 2, NewCells).
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'|'(X, Y, 3, NewCells) :- '|'(X, Y, 1, NewCells).
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'|'(X, Y, 1, [X1-Y-0, X2-Y-2]) :- X1 is X + 1, X2 is X - 1.
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'-'(X, Y, 1, NewCells) :- '.'(X, Y, 1, NewCells).
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'-'(X, Y, 3, NewCells) :- '.'(X, Y, 3, NewCells).
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'-'(X, Y, 2, NewCells) :- '-'(X, Y, 0, NewCells).
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'-'(X, Y, 0, [X-Y1-1, X-Y2-3]) :- Y1 is Y - 1, Y2 is Y + 1.
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replace(I, List, Elem, NewList) :-
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nth0(I, List, _, Rest),
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nth0(I, NewList, Elem, Rest).
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% Input stuff. Cell-(N,E,S,W) indicating which direction was already handled
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input(Name, Map) :- phrase_from_file(lines(Map), Name).
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lines([]) --> eos, !.
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lines([Line|Lines]) --> line(Line), lines(Lines).
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line([]) --> ("\n"; eos), !.
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line([Char-[0,0,0,0]|Chars]) --> [C], line(Chars), {char_code(Char, C)}.
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eos([], []).
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% Debug stuff
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print(Map) :- maplist([X]>>(write(X), nl), Map), nl.
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