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48 lines
1.5 KiB
OCaml
48 lines
1.5 KiB
OCaml
(* Common util. Should probably put this in a module or something.. *)
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let get_one_line file =
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try Some (input_line file) with
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End_of_file -> None
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let get_lines file =
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let rec input lines =
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match get_one_line file with
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Some line -> input (line :: lines)
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| None -> List.rev lines
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in input []
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let read_file file =
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let channel = open_in(file) in
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get_lines channel
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let explode s = (* convert a string to a list of chars *)
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let rec exp i l =
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if i < 0 then l else exp (i - 1) (s.[i] :: l) in
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exp (String.length s - 1) [];;
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(* --- *)
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let wrapped_y y map = (* wrap the y (horizontal) coordinate when off the map *)
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y mod (List.length (List.nth map 1))
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let read_cell map x y = (* return Some char at these coordinates, or None if below the map *)
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if (x < List.length map)
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then Some (List.nth (List.nth map x) (wrapped_y y map))
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else None
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let rec go map position slope = (* move across the map, counting trees *)
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let (x, y) = position in
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let (dy, dx) = slope in (* suddenly regretting having x be the vertical axis.. *)
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match read_cell map x y with
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| None -> 0 (* off the map! stop counting *)
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| Some '#' -> 1 + go map (x+dx, y+dy) slope
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| Some a -> go map (x+dx, y+dy) slope
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let map = read_file "day3.txt" |> List.map explode
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let slopes = [(1, 1); (3, 1); (5, 1); (7, 1); (1, 2)]
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let tree_counts = slopes |> List.map (fun slope -> go map (0, 0) slope);;
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List.iter (fun count -> Printf.printf "Number of trees: %i\n" count) tree_counts;;
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let product = List.fold_left ( * ) 1 tree_counts;;
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Printf.printf "Product: %i\n" product
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