85 lines
2.1 KiB
OCaml
85 lines
2.1 KiB
OCaml
open Containers
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let crane_drop stacks index boxes = stacks.(index) <- boxes @ stacks.(index)
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let crane_lift stacks index count =
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let stack = stacks.(index) in
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let boxes, rest = List.take_drop count stack in
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stacks.(index) <- rest;
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boxes
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;;
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let crane_move1 stacks (count, lift, drop) =
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List.iter
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(fun _ ->
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let box = crane_lift stacks lift 1 in
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crane_drop stacks drop box)
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List.Infix.(0 --^ count)
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;;
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let crane_move stacks (count, lift, drop) =
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let boxes = crane_lift stacks lift count in
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crane_drop stacks drop boxes
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;;
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let init_stacks lines =
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let stacks = Array.init 10 (fun _ -> []) in
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let rec parse_line index line =
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let chunk, rest = String.take_drop 4 line in
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match%pcre chunk with
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| {|(?<letter>\w)|} ->
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crane_drop stacks index [ letter ];
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parse_line (index + 1) rest
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| {| |} -> parse_line (index + 1) rest
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| _ -> ()
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in
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List.iter (parse_line 1) (List.rev lines);
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stacks
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;;
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let move_stacks stacks lines crane_move =
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let parse_line =
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function%pcre
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| {|move (?<count>\d+) from (?<lift>\d+) to (?<drop>\d+)|} ->
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int_of_string count, int_of_string lift, int_of_string drop
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| line -> failwith @@ Printf.sprintf "could not parse line '%s'" line
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in
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List.iter
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(fun line ->
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let instructions = parse_line line in
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crane_move stacks instructions)
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lines
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;;
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let parse_input lines =
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let init_lines, lines = List.take_drop_while (String.starts_with ~prefix:"[") lines in
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let move_lines = List.drop_while Fun.(not % String.starts_with ~prefix:"move") lines in
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init_lines, move_lines
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;;
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let solve crane_move =
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let init_lines, move_lines = parse_input @@ Utils.lines_of_input 5 in
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let stacks = init_stacks init_lines in
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let () = move_stacks stacks move_lines crane_move in
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Array.fold_left
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(fun acc stack ->
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match stack with
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| top :: _ -> acc ^ top
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| [] -> acc)
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""
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stacks
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;;
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let part1 () = solve crane_move1
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let part2 () = solve crane_move
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let%expect_test "Day 5.1" =
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Printf.printf "%s" @@ part1 ();
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[%expect {| PSNRGBTFT |}]
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;;
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let%expect_test "Day 5.2" =
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Printf.printf "%s" @@ part2 ();
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[%expect {| BNTZFPMMW |}]
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;;
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