39 lines
891 B
Perl
39 lines
891 B
Perl
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read_file(Stream, []) :-
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at_end_of_stream(Stream).
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read_file(Stream, [(Cmd, N)|L]) :-
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\+ at_end_of_stream(Stream),
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read_line_to_codes(Stream, C),
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string_chars(S, C),
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split_string(S, " ", "", [S0, S1]),
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atom_string(Cmd, S0),
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number_string(N, S1),
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read_file(Stream, L).
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main :-
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open('../input/02', read, Stream),
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read_file(Stream, Lines), !,
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close(Stream),
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step(Lines, X, Y),
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Z is X * Y,
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print((X, Y, Z)).
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step(Commands, X, Y) :-
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step_(Commands, 0, 0, 0, X, Y).
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step_([], _, X0, Y0, X0, Y0).
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step_([(forward, N)|Tail], Aim, X0, Y0, X, Y) :-
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X1 is X0 + N,
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Y1 is Y0 + N * Aim,
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step_(Tail, Aim, X1, Y1, X, Y).
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step_([(up, N)|Tail], Aim, X0, Y0, X, Y) :-
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Aim1 is Aim - N,
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step_(Tail, Aim1, X0, Y0, X, Y).
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step_([(down, N)|Tail], Aim, X0, Y0, X, Y) :-
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Aim1 is Aim + N,
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step_(Tail, Aim1, X0, Y0, X, Y).
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