145 lines
3.0 KiB
OCaml
145 lines
3.0 KiB
OCaml
let get_range str =
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let list = (String.split_on_char '-' str)
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|> List.map int_of_string in
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assert (List.length list == 2);
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let lower = List.nth list 0 in
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let upper = List.nth list 1 in
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(lower, upper)
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let is_item_in_range i (lower, upper) =
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lower <= i && i <= upper
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let rec list_some l fn =
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match l with
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| [] -> false
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| head :: tail -> if fn head then true else list_some tail fn
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let is_item_in_ranges ranges i =
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list_some ranges (is_item_in_range i)
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let is_overlapping (lower1, upper1) (lower2, upper2) =
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lower1 <= lower2 && lower2 <= upper1 ||
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lower2 <= lower1 && lower1 <= upper2
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let get_combined_ranges (lower1, upper1) (lower2, upper2) =
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let lower = min lower1 lower2 in
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let upper = max upper1 upper2 in
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(lower, upper)
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let non_overlapping_ranges_work ranges =
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let rec loop acc changes ranges =
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match ranges with
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| [] -> (acc, changes)
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| head :: tail ->
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let overlap_fn = is_overlapping head in
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let overlapping_index = List.find_index overlap_fn tail in
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match overlapping_index with
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| Some r ->
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let (l, u) = List.nth tail r in
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let tail_without_index = List.filter
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(fun (lower, upper) -> not (lower == l && upper == u)) tail in
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let combined_range = get_combined_ranges head (l, u) in
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loop (combined_range :: acc) true (tail_without_index)
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| None -> loop (head :: acc) changes tail
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in
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loop [] false ranges
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(* let rec print_ranges l = *)
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(* match l with *)
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(* | [] -> print_endline ""; *)
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(* | (lower, upper) :: tail -> *)
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(* Printf.printf "lower=%d,upper=%d\n" lower upper; *)
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(* print_ranges tail *)
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let rec non_overlapping_ranges ranges =
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let (ranges, changes) = non_overlapping_ranges_work ranges in
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if changes then non_overlapping_ranges ranges
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else ranges
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let solve lines =
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let no_empty_lines = List.filter (fun i -> String.length i > 0) lines in
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let (ranges, items) = List.partition (fun i -> String.contains i '-') no_empty_lines in
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let ranges = List.map get_range ranges in
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let items = List.map int_of_string items in
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let part1 = List.fold_left (
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fun acc i -> if is_item_in_ranges ranges i then acc + 1 else acc
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) 0 items in
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let ranges = non_overlapping_ranges ranges in
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let part2 = List.fold_left (
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fun acc (lower, upper) -> acc + (upper - lower + 1)
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) 0 ranges 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 5";
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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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