(* Baseline: count anagram groups using Hashtbl + sort *)

(* Sort the chars in a string to get its anagram-equivalence key *)
let canonical s =
  let n = String.length s in
  let chars = ref [] in
  for i = 0 to n - 1 do
    chars := (String.get s i) :: !chars
  done ;
  let sorted = List.sort compare !chars in
  String.concat "" sorted
;;

let count_groups words =
  let counts = Hashtbl.create 16 in
  List.iter
    (fun w ->
      let k = canonical w in
      match Hashtbl.find_opt counts k with
      | None -> Hashtbl.add counts k 1
      | Some n -> Hashtbl.replace counts k (n + 1))
    words ;
  Hashtbl.length counts
;;

count_groups ["eat"; "tea"; "tan"; "ate"; "nat"; "bat"]