My yearly advent-of-code solutions
treybastian.com
1let filename = "./day_03_input.txt"
2let try_read ic = try Some (input_line ic) with End_of_file -> None
3
4let read_file ic =
5 let rec read acc =
6 match try_read ic with
7 | Some line -> read (line :: acc)
8 | None ->
9 close_in ic;
10 acc
11 in
12 read [] |> List.rev |> String.concat ""
13
14let regex_mul = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))"
15let regex_mul_part_2 = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))\\|don't()"
16let regex_do_part_2 = Str.regexp "do()"
17
18let calculate_total str regexp =
19 let rec calculate str regexp acc =
20 try
21 let _ = Str.search_forward regexp str 0 in
22 let cmd = Str.matched_group 0 str in
23 let new_str =
24 String.sub str (Str.match_end ()) (String.length str - Str.match_end ())
25 in
26 match cmd with
27 | "do()" -> calculate new_str regex_mul_part_2 acc
28 | "don't()" -> calculate new_str regex_do_part_2 acc
29 | cmd when String.starts_with ~prefix:"mul" cmd ->
30 let a = Str.matched_group 1 str |> int_of_string in
31 let b = Str.matched_group 2 str |> int_of_string in
32 calculate new_str regexp (acc + (a * b))
33 | _ -> acc
34 with Not_found -> acc
35 in
36 calculate str regexp 0
37
38let () =
39 let ic = open_in filename in
40 let data = read_file ic in
41 calculate_total data regex_mul |> Printf.sprintf "Sum %d" |> print_endline;
42
43 calculate_total data regex_mul_part_2
44 |> Printf.sprintf "Part 2 Sum %d"
45 |> print_endline