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(*
* SPDX-FileCopyrightText: Copyright 2025 Alexandre Jesus <https://adbjesus.com>
*
* SPDX-License-Identifier: GPL-3.0-or-later
*)
let solve transition_fn answer_fn ch =
(* the following assumes tachyon splitters are not adjacent *)
(* it also assume that the input is a perfect grid *)
let lines = In_channel.input_lines ch in
let start = String.index (List.hd lines) 'S' in
let m = String.length (List.hd lines) in
let cur = Array.make m 0 in
cur.(start) <- 1;
List.iter (String.iteri (transition_fn cur)) (List.tl lines);
Printf.printf "%d\n" (answer_fn cur)
let part1 ch =
let ans = ref 0 in
let transition_fn cur j c =
if c = '^' then (
cur.(j - 1) <- Int.logor cur.(j - 1) cur.(j);
cur.(j + 1) <- Int.logor cur.(j + 1) cur.(j);
ans := !ans + cur.(j);
cur.(j) <- 0)
in
let answer_fn _cur = !ans in
solve transition_fn answer_fn ch
let part2 ch =
let transition_fn cur j c =
if c = '^' then (
cur.(j - 1) <- cur.(j - 1) + cur.(j);
cur.(j + 1) <- cur.(j + 1) + cur.(j);
cur.(j) <- 0)
in
let answer_fn cur = Array.fold_left ( + ) 0 cur in
solve transition_fn answer_fn ch
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