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(*
* SPDX-FileCopyrightText: Copyright 2025 Alexandre Jesus <https://adbjesus.com>
*
* SPDX-License-Identifier: GPL-3.0-or-later
*)
let part1 ch =
let ops, nums =
In_channel.input_all ch
|> String.trim
|> String.split_on_char '\n'
|> List.map (String.split_on_char ' ')
|> List.map (List.filter (( <> ) ""))
|> List.rev
|> fun l -> (List.hd l, List.map (List.map int_of_string) (List.tl l))
in
List.fold_left
(fun acc l -> List.map2 (fun (r, op) v -> (op r v, op)) acc l)
(List.map (fun o -> if o = "*" then (1, ( * )) else (0, ( + ))) ops)
nums
|> List.map fst
|> List.fold_left ( + ) 0
|> Printf.printf "%d\n"
let part2 ch =
(* another option would be to tranpose the numbers, but I wanted to avoid it *)
let parse_nums lines =
let czero = Char.code '0' in
let parse_digit c = if c = ' ' then None else Some (Char.code c - czero) in
let rec fn nums line =
match (nums, Seq.uncons line) with
| [], None -> []
| nums, None -> nums
| [], Some (v, tv) -> parse_digit v :: fn [] tv
| n :: tn, Some (v, tv) -> (
match (n, parse_digit v) with
| Some n, Some v -> Some ((n * 10) + v) :: fn tn tv
| Some n, None -> Some n :: fn tn tv
| None, Some v -> Some v :: fn tn tv
| None, None -> None :: fn tn tv)
in
List.fold_left (fun acc line -> fn acc (String.to_seq line)) [] lines
|> List.fold_left
(fun acc n ->
match n with
| None -> [] :: acc
| Some n -> (n :: List.hd acc) :: List.tl acc)
[ [] ]
|> List.filter (( <> ) [])
|> List.rev
in
let parse_ops line =
String.split_on_char ' ' line |> List.filter (( <> ) "")
in
let data = In_channel.input_all ch in
let lines = data |> String.split_on_char '\n' |> List.filter (( <> ) "") in
let rlines = List.rev lines in
let ops = parse_ops (List.hd rlines) in
let nums = parse_nums (List.rev (List.tl rlines)) in
List.map2
(fun op nums ->
if op = "*" then List.fold_left ( * ) 1 nums
else List.fold_left ( + ) 0 nums)
ops nums
|> List.fold_left ( + ) 0
|> Printf.printf "%d\n"
|
