Gah. Prolog is hard. I'm not able to find logic programming solutions to these, so I'm just doing it like I would in any other language, which is sort of defeating the point. I may go back and redo days 1 and 2, now that I understand Prolog a bit more, I'm sure I can do those better.
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*.txt
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.DS_Store
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file_to_lines(Path, Lines) :-
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read_file_to_string(Path, S, []),
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split_string(S, "\n", "\n", Lines).
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% Convert "L68" into the tuple l-68
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line_to_turn(Turn, Dir-Dist) :-
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sub_atom(Turn, 0, 1, Len, Dir0),
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sub_string(Turn, 1, Len, _, Dist0),
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number_string(Dist, Dist0),
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downcase_atom(Dir0, Dir).
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main :-
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file_to_lines("data.txt", Lines),
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maplist(line_to_turn, Lines, Turns),
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part1(50, 0, Turns, Res),
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writeln(Res),
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part2(50, 0, Turns, Res2),
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writeln(Res2).
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% PART 1
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turn_knob(Start, Dir-Dist, Result) :-
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Dir = l
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-> Result is (Start - Dist) mod 100
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; Result is (Start + Dist) mod 100.
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% recursion base case, if list is empty, unify the NumZeros with the Result
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part1(_, Res, [], Res).
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% recurse through the list, turning the knob, counting zeros
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part1(Start, NumZeros, [Turn|Rest], Res) :-
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turn_knob(Start, Turn, NewStart),
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(NewStart = 0
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-> NewNumZeros is NumZeros + 1,
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part1(NewStart, NewNumZeros, Rest, Res)
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; part1(NewStart, NumZeros, Rest, Res)).
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% PART 2
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% 6225 too low
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% 6323 too high
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% 6238 wrong
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turn_knob_count_zeros(Start, Dir-Dist, Result, Zeros) :-
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( Dir = l -> Diff is -Dist ; Diff is Dist ),
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Next is Start + Diff,
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divmod(Next, 100, Zeros0, Result0),
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Result is ((Result0 mod 100) + 100) mod 100, % normalize result
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Zeros1 is abs(Zeros0),
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(Start = 0, Dir = l, Dist < 100 -> Zeros2 is Zeros1 - 1 ; Zeros2 is Zeros1),
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(Next = 0 -> Zeros is Zeros2 + 1 ; Zeros = Zeros2),
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format('Start: ~w Dir: ~w Dist: ~w Next: ~w Result: ~w Zeros: ~w~n',
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[Start, Dir, Dist, Next, Result, Zeros]).
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part2(_, Res, [], Res).
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part2(Start, NumZeros, [Turn|Rest], Res) :-
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turn_knob_count_zeros(Start, Turn, NewStart, Zeros),
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NewNumZeros is Zeros + NumZeros,
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format('New Zeros ~w~n', NewNumZeros),
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part2(NewStart, NewNumZeros, Rest, Res).
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/*
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Start: 0 Dir: l Dist: 223 Next: -223 Result: 77 Zeros: 3
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Start: 52 Dir: r Dist: 192 Next: 244 Result: 44 Zeros: 2
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*/
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file_to_ranges(Path, Ranges) :-
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read_file_to_string(Path, S, []),
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split_string(S, ",", ",", Ranges).
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range_to_tuple(Range, Start-End) :-
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split_string(Range, "-", "\n", [Start0|[End0]]),
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number_string(Start, Start0),
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number_string(End, End0).
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is_even(N) :- integer(N), mod(N, 2) =:= 0.
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main :-
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file_to_ranges("data.txt", Ranges),
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maplist(range_to_tuple, Ranges, Tuples),
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% Part 1
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maplist(find_invalids_part1, Tuples, InvalidsPart1Unflattened),
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flatten(InvalidsPart1Unflattened, InvalidsPart1),
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sumlist(InvalidsPart1, Part1Sum),
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write("Part 1: "),
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writeln(Part1Sum),
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% Part 2
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maplist(find_invalids_part2, Tuples, InvalidsPart2Unflattened),
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flatten(InvalidsPart2Unflattened, InvalidsPart2),
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sumlist(InvalidsPart2, Part2Sum),
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write("Part 2: "),
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writeln(Part2Sum).
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% Part 1
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find_invalids_part1(Start-End, Invalids) :-
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numlist(Start, End, Numbers),
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include(is_invalid_part1, Numbers, Invalids).
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is_invalid_part1(Number) :-
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number_string(Number, String),
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string_length(String, Len),
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(is_even(Len) ->
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Len2 is Len / 2,
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sub_string(String, 0, Len2, _, Start),
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sub_string(String, Len2, Len2, _, End),
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Start = End
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; false).
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% Part 2
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find_invalids_part2(Start-End, Invalids) :-
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numlist(Start, End, Numbers),
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include(is_invalid_part2, Numbers, Invalids).
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is_invalid_part2(Number) :-
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number_string(Number, String),
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string_length(String, FullLength),
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SubLenMax is floor(FullLength / 2),
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numlist(1, SubLenMax, Lengths),
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maplist(generate_substrings(String), Lengths, Subs),
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include(is_made_of_subs(String), Subs, Results),
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length(Results, L),
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L > 0.
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generate_substrings(S, Len, Sub) :- sub_string(S, 0, Len, _, Sub).
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% don't want to try to do this smartly, let's just check a bunch
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is_made_of_subs(String, Sub) :-
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string_concat(Sub, Sub, Twice),
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string_concat(Twice, Sub, Thrice),
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string_concat(Thrice, Sub, FourTimes),
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string_concat(FourTimes, Sub, FiveTimes),
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string_concat(FiveTimes, Sub, SixTimes),
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string_concat(SixTimes, Sub, SevenTimes),
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(
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String = Twice;
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String = Thrice;
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String = FourTimes;
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String = FiveTimes;
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String = SixTimes;
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String = SevenTimes
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).
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:- use_module(library(lists)).
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main :-
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File = "data.txt",
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run(File, 2, Part1),
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writeln(Part1),
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run(File, 12, Part2),
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writeln(Part2).
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file_bank(Path, Bank) :-
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read_file_to_string(Path, S, []),
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split_string(S, "\n", "\n", Lines),
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member(Line, Lines),
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number_string(Number, Line),
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number_chars(Number, Chars),
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maplist(atom_number, Chars, Bank).
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run(Path, DigitSize, Sum) :-
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findall(N,
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(file_bank(Path, Bank), bank_max(Bank, DigitSize, N)),
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Ns),
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sumlist(Ns, Sum).
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bank_max(Bank, DigitSize, Max) :-
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bank_max_acc(Bank, DigitSize, [], Answer),
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list_to_number(Answer, Max).
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bank_max_acc(_, 0, NumList, NumList).
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bank_max_acc(Bank, DigitsLeft, NumList, Answer) :-
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length(Bank, Len),
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SplitIndex is Len - DigitsLeft + 1,
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split_list_at_index(Bank, SplitIndex, Left, _),
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max_list(Left, Digit),
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nth0(FoundIndex, Left, Digit),
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DigitsLeft2 is DigitsLeft - 1,
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append(NumList, [Digit], NumList2),
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NewSplitIndex is FoundIndex + 1,
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split_list_at_index(Bank, NewSplitIndex, _, Rest),
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bank_max_acc(Rest, DigitsLeft2, NumList2, Answer),
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!.
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% Helpers
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split_list_at_index(List, Index, Left, Right) :-
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length(Left, Index),
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append(Left, Right, List).
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list_to_number(Digits, Number) :- list_to_number_acc(Digits, 0, Number).
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list_to_number_acc([], Acc, Acc).
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list_to_number_acc([Digit|Rest], AccIn, Number) :-
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AccNext is AccIn * 10 + Digit,
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list_to_number_acc(Rest, AccNext, Number).
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