27 lines
850 B
OCaml
27 lines
850 B
OCaml
(** [is_monotonic pred lst] returns true if [pred] returns true when tested on
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all consecutive elements of [lst]. *)
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let rec is_monotonic pred = function
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| [] | _ :: [] -> true
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| h :: h' :: t -> pred h h' && is_monotonic pred (h' :: t)
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let is_safe lst =
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(is_monotonic ( < ) lst || is_monotonic ( > ) lst)
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&& is_monotonic (fun a b -> Aoc.distance1 a b <= 3) lst
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let is_safe_dampened lst =
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let rec impl acc = function
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| [] -> is_safe acc
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| h :: t -> is_safe (acc @ t) || impl (acc @ [ h ]) t
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in
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impl [] lst
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let nums_from_file fname =
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Aoc.strings_from_file fname |> List.map Aoc.nums_from_string
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let day2402a lsts = List.filter is_safe lsts |> List.length
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let day2402b lsts = List.filter is_safe_dampened lsts |> List.length
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let _ =
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Aoc.main nums_from_file
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[ (string_of_int, day2402a); (string_of_int, day2402b) ]
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