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(*
* SPDX-FileCopyrightText: Copyright 2025 Alexandre Jesus <https://adbjesus.com>
*
* SPDX-License-Identifier: GPL-3.0-or-later
*)
let parse_range s =
match String.split_on_char '-' s with
| [ a; b ] -> (int_of_string a, int_of_string b)
| _ -> failwith ("Invalid range " ^ s)
let parse_ranges ch =
In_channel.input_all ch
|> String.trim
|> String.split_on_char ','
|> List.map parse_range
let is_invalid s cnt =
cnt > 0
&& String.length s mod cnt = 0
&& String.to_seqi s
|> Seq.drop cnt
|> Seq.for_all (fun (i, c) -> c = s.[i - cnt])
let is_invalid_part1 a =
let s = string_of_int a in
let l = String.length s in
is_invalid s (l / 2)
let sum_invalid_ids invalid_fn (a, b) =
Seq.ints a
|> Seq.take (b - a + 1)
|> Seq.filter invalid_fn
|> Seq.fold_left ( + ) 0
let solve ch invalid_fn =
parse_ranges ch
|> List.map (sum_invalid_ids invalid_fn)
|> List.fold_left ( + ) 0
|> Printf.printf "%d\n"
let part1 ch = solve ch is_invalid_part1
let is_invalid_part2 a =
let s = string_of_int a in
let l = String.length s in
Seq.ints 1 |> Seq.take (l / 2) |> Seq.exists (is_invalid s)
let part2 ch = solve ch is_invalid_part2
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