aoc2022/day7.m

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:- module day7.
:- interface.
:- import_module basics.
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:- pred run(part::in, lines::in, answer::out) is cc_multi.
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:- implementation.
:- import_module int.
:- import_module string.
:- import_module list.
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:- type dir ---> dir(size :: int, dirs :: dirs).
:- func size(dir) = int.
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:- type dirs == list(dir).
:- pred dir(dir::out, lines::in, lines::out) is nondet.
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dir(dir(Size, Dirs)) -->
[Cd], {append("$ cd ", _, Cd)},
["$ ls"],
files(Files),
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dirs(Dirs),
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{Size = Files + sum(map(size, Dirs))},
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(["$ cd .."] ; []).
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:- pred files(int::out, lines::in, lines::out) is multi.
files(Size + Rest) -->
[Line], {to_int(head(words(Line)), Size)},
files(Rest).
files(Size) -->
[Dir], {append("dir ", _, Dir)},
files(Size).
files(0) --> [].
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:- pred dirs(dirs::out, lines::in, lines::out) is multi.
dirs([D | Ds]) --> dir(D), dirs(Ds).
dirs([]) --> [].
:- pred find(pred(dir)::(pred(in) is semidet), dir::in, list(dir)::out) is det.
find(P, Dir, Out) :-
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map(find(P), dirs(Dir), Outs), Children = condense(Outs),
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(if P(Dir) then Out = [Dir | Children] else Out = Children).
:- pred size_lte(int::in, dir::in) is semidet.
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size_lte(Size, Dir) :- size(Dir) =< Size.
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:- pred size_gte(int::in, dir::in) is semidet.
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size_gte(Size, Dir) :- size(Dir) >= Size.
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:- pred go(part::in, dir::in, int::out) is det.
go(one, Top, sum(map(size, Found))) :-
find(size_lte(100_000), Top, Found).
go(two, Top, det_head(sort(map(size, Found)))) :-
find(size_gte(size(Top) - 40_000_000), Top, Found).
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run(Part, Lines, int(Out)) :-
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if dir(Top, Lines, []) then go(Part, Top, Out) else die("bad input").