bruteforce_cpf.ml

let valid_cpf cpf =
  let aux size =
    let sum = ref 0 in
    for i = 0 to (size - 2) do
      sum := !sum + cpf.(i) * (size - i);
    done;
    !sum * 10 mod 11
  in
  (aux 10) == cpf.(9) && (aux 11) == cpf.(10)

let join sep a =
  Array.fold_left (fun acc value -> acc ^ sep ^ value) "" a

let print_array a =
  a |> join " " |> print_endline;

exception Break
let next digits =
  try
    for i = 8 downto 0 do
      if (digits.(i) < 9) then begin
        digits.(i) <- digits.(i) + 1;
        raise Break
      end else begin
        digits.(i) <- 0;
      end
    done
  with Break -> ()

let should_stop digits =
  Array.sub digits 0 9 
  |> Array.for_all (fun d -> d == 9)

let () =
  let digits = [| 7; 4 |] in
  let base = [| 0; 0; 0; 0; 0; 0; 0; 0; 0 |] in
  let cpf = Array.append base digits in

  let tries = ref 0 in
  let count = ref 0 in

  while not (should_stop cpf) do
    cpf |> Array.map string_of_int |> print_array;

    if valid_cpf cpf then
      incr count;

    incr tries;
    next cpf;
  done;

  Printf.printf "Found %d, Tried: %d\n" !count !tries;