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|
let filename = "./day_03_input.txt"
let try_read ic = try Some (input_line ic) with End_of_file -> None
let read_file ic =
let rec read acc =
match try_read ic with
| Some line -> read (line :: acc)
| None ->
close_in ic;
acc
in
read [] |> List.rev |> String.concat ""
let regex_mul = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))"
let regex_mul_part_2 = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))\\|don't()"
let regex_do_part_2 = Str.regexp "do()"
let calculate_total str regexp =
let rec calculate str regexp acc =
try
let _ = Str.search_forward regexp str 0 in
let cmd = Str.matched_group 0 str in
let new_str =
String.sub str (Str.match_end ()) (String.length str - Str.match_end ())
in
match cmd with
| "do()" -> calculate new_str regex_mul_part_2 acc
| "don't()" -> calculate new_str regex_do_part_2 acc
| cmd when String.starts_with ~prefix:"mul" cmd ->
let a = Str.matched_group 1 str |> int_of_string in
let b = Str.matched_group 2 str |> int_of_string in
calculate new_str regexp (acc + (a * b))
| _ -> acc
with Not_found -> acc
in
calculate str regexp 0
let () =
let ic = open_in filename in
let data = read_file ic in
calculate_total data regex_mul |> Printf.sprintf "Sum %d" |> print_endline;
calculate_total data regex_mul_part_2
|> Printf.sprintf "Part 2 Sum %d"
|> print_endline
|
