advent_of_code_2019_4.ml

let increasing (chr_lst : char list) =
  List.fold_left
    (fun last_int chr ->
      if last_int >= 0 then
        let chr_int = int_of_string (String.make 1 chr) in
        if last_int <= chr_int then
          chr_int
        else
          (-1)
      else
        last_int)
    0
    chr_lst

let consecutive (chr_lst : char list) =
  List.fold_left
    (fun (last_int, tmp_cnt, cnt, cnt_lst) chr ->
      let chr_int = int_of_string (String.make 1 chr) in
      (* Printf.printf "last_int: %d ; tmp_cnt: %d ; cnt: %d | cur_chr: %d\n"
       *   last_int tmp_cnt cnt chr_int ; *)
      if last_int = chr_int then
        if cnt <= (tmp_cnt + 1) then
          (last_int, (tmp_cnt + 1), (tmp_cnt + 1), cnt_lst)
        else
          (last_int, (tmp_cnt + 1), cnt, cnt_lst)
      else
        (chr_int, 0, cnt, tmp_cnt :: cnt_lst)
    )
    (0, 0, 0, [])
    chr_lst
  
let satisfy_rules (p : string) =
  if (String.length p) = 6 then
    let p_lst = List.init (String.length p) (String.get p) in
    let is_increasing = increasing p_lst and
        (_, tmp_cnt, consec_cnt, consec_cnt_lst1) = consecutive p_lst in
    let consec_cnt_lst = tmp_cnt :: (consec_cnt :: consec_cnt_lst1) in
    let double_grp = List.filter
                       (fun v -> if v = 1 then true else false)
                       consec_cnt_lst in
    (* Printf.printf "increasing: %d consec_cnt: %d\n" is_increasing consec_cnt ; *)
    (* List.iter (Printf.printf "%d ") consec_cnt_lst ; *)
    if is_increasing >= 0 && (List.length double_grp) > 0 then
      true
    else
      false                      
  else
    false

let main (start : int) (fin : int) =
  let cnt = ref 0 in
  for num = start to fin do
    if satisfy_rules (string_of_int num) then
      cnt := !cnt + 1
  done ;
  Printf.printf "count: %d\n" !cnt

let () = main 138241 674034