60 lines
1.3 KiB
OCaml
60 lines
1.3 KiB
OCaml
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type space = Tree | Free
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type map = space array array
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let (.%()) arr i = arr.(i mod Array.length arr)
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let iter_map ?(step_x=1) ?(step_y=1) f arr =
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let i = ref 0 in
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let j = ref 0 in
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while !i < Array.length arr do
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f arr.(!i).%(!j);
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i := !i + step_x;
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j := !j + step_y
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done
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exception Unknown_char of char
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let make_line str =
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Array.init (String.length str)
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(fun i -> match str.[i] with
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| '#' -> Tree
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| '.' -> Free
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| c -> raise (Unknown_char c))
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let read_file = Bracket.infile_lines ~line:make_line ~of_seq:Array.of_seq
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let count_trees ?step_x ?step_y map =
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let count = ref 0 in
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iter_map ?step_x ?step_y (function Tree -> incr count | _ -> ()) map;
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!count
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let main1 input =
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Format.printf "%d trees\n"
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(count_trees ~step_y:3 (read_file input))
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let main2 input =
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let map = read_file input in
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let prod = List.fold_left ( * ) 1
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[count_trees map;
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count_trees map ~step_y:3;
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count_trees map ~step_y:5;
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count_trees map ~step_y:7;
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count_trees map ~step_x:2] in
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Format.printf "product: %d\n" prod
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let mains = [|main1; main2|]
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let main = function
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| [part; input] -> mains.(int_of_string part - 1) input
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| _ -> failwith "a"
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let%expect_test _ =
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main1 "../../data/day3";
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[%expect{| 244 trees |}]
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let%expect_test _ =
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main2 "../../data/day3";
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[%expect{| product: 9406609920 |}]
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