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49 lines
2.0 KiB
49 lines
2.0 KiB
-module(day5).
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-compile(export_all).
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-export([solve/1]).
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solve(InputData) ->
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[DiagramData, Instructions] = binary:split(InputData, <<"\n\n">>, [trim_all]),
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Diagram = lists:reverse(binary:split(DiagramData, <<"\n">>, [trim_all, global])),
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Stacks = parse_diagram(Diagram),
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EndStacks = eval_instructions(Instructions, Stacks),
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{print_stacks(EndStacks), none}.
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print_stacks(Stacks) ->
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lists:reverse(
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maps:fold(fun (_Key, [Top|_Rest], Acc) -> [Top|Acc] end, [], Stacks)
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).
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eval_instructions(<<>>, Stacks) -> Stacks;
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eval_instructions(Instructions, Stacks) ->
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<<"move ", Instruction1/binary>> = Instructions,
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{Moves, Instruction2} = parse_int(Instruction1),
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<<" from ", DigitFrom, " to ", DigitTo, $\n, Rest/binary>> = Instruction2,
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eval_instructions(Rest, eval_move(DigitFrom, DigitTo, Moves, Stacks)).
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parse_int(String) -> parse_int(String, 0).
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parse_int(<<Char, Rest/binary>>, Acc) when Char >= $0 andalso Char =< $9 -> parse_int(Rest, Acc*10+(Char - $0));
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parse_int(String, Acc) -> {Acc, String}.
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eval_move(_DigitFrom, _DigitTo, 0, Stacks) -> Stacks;
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eval_move(DigitFrom, DigitTo, N, Stacks) when is_integer(N) and (N > 0) ->
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#{DigitFrom := [Item | StackFrom], DigitTo := StackTo} = Stacks,
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eval_move(DigitFrom, DigitTo, N-1, Stacks#{DigitFrom := StackFrom, DigitTo := [Item | StackTo]}).
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parse_diagram([Program | Boxes]) -> parse_diagram(Program, Boxes, #{}).
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parse_diagram(<<>>, _Boxes, Stacks) -> Stacks;
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parse_diagram(<<Digit, ProgramRest/binary>>, Boxes, Stacks) when Digit >= $0 andalso Digit =< $9 ->
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parse_diagram(
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ProgramRest,
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lists:map(fun(<<_, Tail/binary>>) -> Tail end, Boxes),
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Stacks#{Digit => build_stack(Boxes, [])}
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);
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parse_diagram(<<_Char, ProgramRest/binary>>, Boxes, Stacks) ->
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parse_diagram(ProgramRest, lists:map(fun(<<_, Tail/binary>>) -> Tail end, Boxes), Stacks).
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build_stack([], Stack) -> Stack;
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build_stack([<<$\s, _Rest/binary>> | _Rows], Stack) -> Stack;
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build_stack([<<Item, _Rest/binary>> | Rows], Stack) -> build_stack(Rows, [Item | Stack]).
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