let read_file_rev name =
    let ic = open_in name in
    let try_read () =
        try Some (input_line ic)
        with End_of_file -> None in
    let rec loop acc =
        match try_read () with
        | Some s -> loop (s::acc)
        | None -> close_in ic; acc in
    loop []


let count_good_passwords f l =
    let is_conforming f entry =
        let [term; pass] = String.split_on_char ':' entry in
        let [rep; letter] = String.split_on_char ' ' term in
        let [minr; maxr] = List.map int_of_string (String.split_on_char '-' rep) in
        f pass minr maxr letter.[0] in
    List.map (is_conforming f) l
        |> List.map (fun b -> if b then 1 else 0)
        |> List.fold_left (+) 0


let part1_f pass minr maxr letter =
    let count = List.length (String.split_on_char letter pass) - 1 in
    minr <= count && count <= maxr

let part2_f pass first second letter =
    let position_matches pass pos letter =
        match String.get pass pos with
        | c -> c = letter
        | _ -> false in
    (position_matches pass first letter) <> (position_matches pass second letter)


let do_count filename = function
    | 1 -> read_file_rev filename |> count_good_passwords part1_f
    | 2 -> read_file_rev filename |> count_good_passwords part2_f


let () =
    print_endline (string_of_int (do_count "day2.input" 1))

let () =
    print_endline (string_of_int (do_count "day2.input" 2))