let has_repeating_char s =
    let chars = List.init (String.length s) (String.get s) in
    let rec aux = function
        | x :: xs -> List.exists (fun q -> q = x) xs || aux xs
        | [] -> false
    in aux chars

exception NotFound

let calculate_offset offset input =
    let buf = String.sub input 0 offset in
    let rec aux idx buf input =
        if not (has_repeating_char buf) then idx + offset - 1
        else if idx + offset = String.length input then raise NotFound
        else aux (idx + 1) (String.sub input idx offset) input in
    aux 1 buf input

let input = Utils.read_file "bin/d6/input.txt" |> List.hd ;;
"\n1: " ^ (string_of_int (calculate_offset 4 input)) ^
"\n2: " ^ (string_of_int ((calculate_offset 14 input)))
    |> print_endline