59 lines
1.7 KiB
OCaml
59 lines
1.7 KiB
OCaml
let find grid c =
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match Aoc.Grid.idx_from_opt grid 0 c with
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| None -> failwith "find"
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| Some idx -> Aoc.Grid.pos_of_idx grid idx
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let input_of_file fname =
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let grid = Aoc.Grid.of_file fname in
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let start_state = (find grid 'S', (1, 0)) in
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(grid, start_state)
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let rec dijkstra visit check_end states =
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let compare_costs (lhs, _) (rhs, _) = compare lhs rhs in
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match states with
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| [] -> failwith "dijkstra"
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| (cost, state) :: t ->
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if check_end state then cost
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else
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let new_states =
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visit cost state |> List.sort compare_costs
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|> List.merge compare_costs t
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in
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dijkstra visit check_end new_states
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let visited_idx grid (p, (dx, dy)) =
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let add =
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match (dx, dy) with
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| 1, 0 -> 0
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| 0, 1 -> 1
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| -1, 0 -> 2
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| 0, -1 -> 3
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| _ -> failwith "visited_idx"
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in
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(Aoc.Grid.idx_of_pos grid p * 4) + add
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let has_visited grid visited_grid state = visited_grid.(visited_idx grid state)
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let mark_visited grid visited_grid state =
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visited_grid.(visited_idx grid state) <- true
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let visit grid visited_grid cost ((((x, y) as p), (dx, dy)) as state) =
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if has_visited grid visited_grid state then []
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else if Aoc.Grid.get_by_pos grid p = '#' then []
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else (
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Printf.printf "%d %d %d %d %d\n" cost x y dx dy;
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mark_visited grid visited_grid state;
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[
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(cost + 1, ((x + dx, y + dy), (dx, dy)));
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(cost + 1000, (p, (-dy, dx)));
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(cost + 1000, (p, (dy, -dx)));
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])
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let check_end grid (p, _) = Aoc.Grid.get_by_pos grid p = 'E'
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let part (grid, start_state) =
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let visited_grid = Array.make (Aoc.Grid.length grid * 4) false in
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dijkstra (visit grid visited_grid) (check_end grid) [ (0, start_state) ]
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let _ = Aoc.main input_of_file [ (string_of_int, part) ]
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