82 lines
1.9 KiB
Prolog
82 lines
1.9 KiB
Prolog
char(X, L, C0, L, C) -->
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[X0], {X0 \= 0'\n, char_code(X, X0), C is C0 + 1}, !.
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digit(D, L0, C0, L, C) --> char(D, L0, C0, L, C), {char_type(D, digit)}.
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digits([D|Ds], L0, C0, L, C) -->
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digit(D, L0, C0, L1, C1),
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digits0(Ds, L1, C1, L, C).
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digits0(Ds, L0, C0, L, C) --> digits(Ds, L0, C0, L, C).
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digits0([], L, C, L, C) --> [].
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newline(L0, _, L, 0) --> "\n", {L is L0 + 1}.
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num(n(N, L-C0-C1), L, C0, L, C) -->
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digits(Ds, L, C0, L, C), !,
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{number_chars(N, Ds), C1 is C - 1}.
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dot(L0, C0, L, C) --> char('.', L0, C0, L, C).
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sym(s(X, L-C0), L, C0, L, C) -->
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char(X, L, C0, L, C),
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{\+ char_type(X, digit), X \= '.'}.
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thing(X, L0, C0, L, C) --> num(X, L0, C0, L, C).
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thing(X, L0, C0, L, C) --> sym(X, L0, C0, L, C).
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nonthing(L0, C0, L, C) --> dot(L0, C0, L, C).
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nonthing(L0, C0, L, C) --> newline(L0, C0, L, C).
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input([], L, C, L, C) --> [].
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input([I|Is], L0, C0, L, C) -->
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thing(I, L0, C0, L1, C1), !,
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input(Is, L1, C1, L, C).
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input(Is, L0, C0, L, C) -->
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nonthing(L0, C0, L1, C1), !,
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input(Is, L1, C1, L, C).
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input(Is) --> input(Is, 0, 0, _, _).
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adjacent(LN-CN0-CN1, LS-CS) :-
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LLo is LN - 1, LHi is LN + 1, LS >= LLo, LS =< LHi,
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CLo is CN0 - 1, CHi is CN1 + 1, CS >= CLo, CS =< CHi.
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part_number(N) :-
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n(N, NLoc), s(_, SLoc), adjacent(NLoc, SLoc).
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number_next_to(N, SLoc) :-
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n(N, NLoc), adjacent(NLoc, SLoc).
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gear(Ratio) :-
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s('*', SLoc),
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bagof(N, number_next_to(N, SLoc), [A, B]),
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Ratio is A * B.
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parse_setup(File) :- parse(File, Items), setup(Items).
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parse(File, Items) :- phrase_from_file(input(Items), File), !.
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setup(Items) :-
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transaction((abolish(n/2), abolish(s/2), maplist(assert, Items))).
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:- dynamic n/2, s/2.
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sum(Xs, X) :- foldl(plus, Xs, 0, X).
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part1(File) :-
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parse_setup(File),
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bagof(N, part_number(N), Ns),
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sum(Ns, Total),
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writeln(Total).
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part2(File) :-
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parse_setup(File),
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bagof(R, gear(R), Rs),
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sum(Rs, Total),
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writeln(Total).
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% vim: set ft=prolog :
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