87 lines
2.4 KiB
OCaml
87 lines
2.4 KiB
OCaml
let get_highest_number_and_index l =
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let (t, _) = List.fold_left (
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fun ((highest, highest_index), index) i ->
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if i > highest then
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((i, index), index + 1)
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else
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((highest, highest_index), index + 1)
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) ((0, 0), 0) (List.rev l) in
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t
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let rec first_n k xs = match xs with
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| [] -> failwith "firstk"
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| x::xs -> if k=1 then [x] else x::first_n (k-1) xs
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let slice_at_index l index =
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let rec loop (i, acc) =
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match acc with
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| [] -> failwith "too far"
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| _ :: tail -> if i == index then tail else loop (i + 1, tail)
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in
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loop (0, List.rev l)
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let highest_n n l =
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let rec loop acc n l =
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match n with
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| 0 -> acc
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| n ->
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let list_first_n_items = first_n (List.length l - n + 1) (List.rev l) |> List.rev in
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let (highest, highest_index) = get_highest_number_and_index list_first_n_items in
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let remaining_list = slice_at_index l highest_index in
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loop (highest :: acc) (n - 1) (List.rev remaining_list)
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in
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loop [] n l
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let string_to_int_list l =
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l
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|> String.to_seq
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|> List.of_seq
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|> List.fold_left (fun acc i -> ((int_of_char i) - (int_of_char '0')) :: acc) []
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let num_from_int_list l =
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let rec loop acc index l =
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match l with
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| [] -> acc
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| head :: tail -> loop (acc + index * head) (index * 10) tail
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in
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loop 0 1 l
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let solve lines =
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let nums_part1 = List.fold_left (
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fun acc line -> (line |> string_to_int_list |> (highest_n 2)) :: acc
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) [] lines in
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let part1 = List.fold_left (+) 0 (List.map num_from_int_list nums_part1) in
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let nums_part2 = List.fold_left (
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fun acc line -> (line |> string_to_int_list |> (highest_n 12)) :: acc
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) [] lines in
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let part2 = List.fold_left (+) 0 (List.map num_from_int_list nums_part2) in
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(part1, part2)
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let read_lines name =
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let ic = open_in name in
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let try_read () = try Some (input_line ic) with End_of_file -> None in
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let rec loop acc =
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match try_read () with
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| Some s -> loop (s :: acc)
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| None ->
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close_in ic;
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List.rev acc
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in
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loop []
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let () =
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print_endline "Day 3";
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let part1, part2 =
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read_lines "./input.txt" |> solve
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in
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Printf.printf "Part 1: %s\nPart 2: %s\n" (string_of_int part1)
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(string_of_int part2)
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