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2024 day 16 part 2

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Quite slow takes ~11 mins to run.
This commit is contained in:
Matthew Gretton-Dann
2024-12-16 11:33:17 +00:00
parent 06c006d5bd
commit bfd65557bf
1 changed files with 63 additions and 21 deletions
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84
bin/day2416.ml
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@@ -5,15 +5,15 @@ let find grid c =
let input_of_file fname =
let grid = Aoc.Grid.of_file fname in
let start_state = (find grid 'S', (1, 0)) in
(grid, start_state)
let start_pos = find grid 'S' in
(grid, start_pos)
let rec dijkstra visit check_end states =
let compare_costs (lhs, _) (rhs, _) = compare lhs rhs in
match states with
| [] -> failwith "dijkstra"
| [] -> None
| (cost, state) :: t ->
if check_end state then cost
if check_end state then Some (cost, state, t)
else
let new_states =
visit cost state |> List.sort compare_costs
@@ -21,7 +21,7 @@ let rec dijkstra visit check_end states =
in
dijkstra visit check_end new_states
let visited_idx grid (p, (dx, dy)) =
let visited_idx grid ((dx, dy), p) =
let add =
match (dx, dy) with
| 1, 0 -> 0
@@ -32,27 +32,69 @@ let visited_idx grid (p, (dx, dy)) =
in
(Aoc.Grid.idx_of_pos grid p * 4) + add
let has_visited grid visited_grid state = visited_grid.(visited_idx grid state)
let mark_visited grid visited_grid state =
visited_grid.(visited_idx grid state) <- true
let visit grid visited_grid cost ((((x, y) as p), (dx, dy)) as state) =
if has_visited grid visited_grid state then []
let visit grid visited_grid cost state =
let (dx, dy), ((x, y) as p) = List.hd state in
let has_visited = visited_grid.(visited_idx grid (List.hd state)) in
if has_visited then []
else if Aoc.Grid.get_by_pos grid p = '#' then []
else (
Printf.printf "%d %d %d %d %d\n" cost x y dx dy;
mark_visited grid visited_grid state;
visited_grid.(visited_idx grid (List.hd state)) <- true;
[
(cost + 1, ((x + dx, y + dy), (dx, dy)));
(cost + 1000, (p, (-dy, dx)));
(cost + 1000, (p, (dy, -dx)));
(cost + 1, ((dx, dy), (x + dx, y + dy)) :: state);
(cost + 1000, ((-dy, dx), p) :: state);
(cost + 1000, ((dy, -dx), p) :: state);
])
let check_end grid (p, _) = Aoc.Grid.get_by_pos grid p = 'E'
let visit_max grid visited_grid max_cost cost state =
let has_visited = visited_grid.(visited_idx grid (List.hd state)) < cost in
let (dx, dy), ((x, y) as p) = List.hd state in
if has_visited then []
else if cost > max_cost then []
else if Aoc.Grid.get_by_pos grid p = '#' then []
else (
(*Printf.printf "%d (%d, %d)\n" cost x y;
flush stdout;*)
visited_grid.(visited_idx grid (List.hd state)) <- cost;
[
(cost + 1, ((dx, dy), (x + dx, y + dy)) :: state);
(cost + 1000, ((-dy, dx), p) :: state);
(cost + 1000, ((dy, -dx), p) :: state);
])
let part (grid, start_state) =
let[@warning "-32"] print_point (x, y) = Printf.printf "(%d, %d)" x y
let check_end grid state =
let _, p = List.hd state in
Aoc.Grid.get_by_pos grid p = 'E'
let check_end2 grid _ state = check_end grid state
let part1 (grid, start_pos) =
let visited_grid = Array.make (Aoc.Grid.length grid * 4) false in
dijkstra (visit grid visited_grid) (check_end grid) [ (0, start_state) ]
match
dijkstra (visit grid visited_grid) (check_end grid)
[ (0, [ ((1, 0), start_pos) ]) ]
with
| None -> failwith "part"
| Some (cost, _, _) -> cost
let _ = Aoc.main input_of_file [ (string_of_int, part) ]
let part2 (grid, start_pos) =
let cost = part1 (grid, start_pos) in
let visited_grid = Array.make (Aoc.Grid.length grid * 4) max_int in
let rec impl acc lst =
match
dijkstra
(visit_max grid visited_grid cost)
(check_end2 grid visited_grid)
lst
with
| None -> acc
| Some (_, states, remainder) ->
List.iter (fun x -> visited_grid.(visited_idx grid x) <- 0) states;
impl (states :: acc) remainder
in
impl [] [ (0, [ ((1, 0), start_pos) ]) ]
|> List.concat |> List.map snd |> List.sort_uniq compare |> List.length
let _ =
Aoc.main input_of_file [ (string_of_int, part1); (string_of_int, part2) ]