day19 shorter

19/main.ml

@@ -13,23 +13,16 @@ let get_input_lists list_of_lines =
   | towels_list :: _ :: tail -> (towels_list, tail)
   | _ -> raise (Invalid_argument "Not enough lines")  
 
-let rec try_any_towel cache towels pattern =
-  towels
+let rec try_construct cache towels pattern =
+  match Hashtbl.find_opt cache pattern with
+  | Some result -> result
+  | None ->
+    let result = towels
       |> List.filter (fun towel -> 
         String.starts_with ~prefix:towel pattern)
       |> List.map (fun towel -> 
         try_construct cache towels (String.sub pattern (String.length towel) (String.length pattern - String.length towel)))
-    |> List.fold_left Int.add 0
-
-and try_construct cache towels pattern =
-  if String.length pattern = 0 then
-    1
-  else
-    match Hashtbl.find_opt cache pattern with
-    | Some result ->
-      result
-    | None ->
-      let result = try_any_towel cache towels pattern in
+      |> List.fold_left Int.add 0 in
     Hashtbl.add cache pattern result;
     result
 
@@ -38,6 +31,7 @@ let () =
   let towels_str, patterns_list = list_of_lines f |> get_input_lists in
   let towels_list = towels_str |> String.split_on_char ',' |> List.map (fun x -> x |> String.trim) in
   let cache = Hashtbl.create 1024 in
+  Hashtbl.add cache "" 1;
   let possibilities_list = patterns_list |> List.map (try_construct cache towels_list) in
   let result = possibilities_list |> List.filter (fun x-> x > 0) |> List.length  in
   let result2 = List.fold_left Int.add 0 possibilities_list in