Move memoize to the Aoc library.

bin/day2419.ml

@@ -14,17 +14,6 @@ let towels_of_file fname = Aoc.strings_of_file fname |> towels_of_strings
 (** Memoizing hash table shared between parts 1 and 2. *)
 let memo = Hashtbl.create 1000
 
-(** [memoize memo f value] returns the result of [f value]. The hashtable [memo]
-    is used to cache results, so repeated calls with the same [value] will not
-    call [f] again. *)
-let memoize memo f value =
-  match Hashtbl.find_opt memo value with
-  | Some x -> x
-  | None ->
-      let x = f value in
-      Hashtbl.add memo value x;
-      x
-
 (** [count_hashes memo towels pattern] counts the number of ways of matching
     [pattern] using [towels]. [memo] is a hashtable used for memoizing results.
 *)
@@ -35,7 +24,7 @@ let rec count_matches memo towels pattern =
     | h :: t ->
         let towel_len = String.length h in
         if String.starts_with ~prefix:h pattern then
-          memoize memo
+          Aoc.memoize memo
             (count_matches memo towels)
             (String.sub pattern towel_len (pattern_len - towel_len))
           + count_matched t
@@ -44,12 +33,12 @@ let rec count_matches memo towels pattern =
   if pattern_len = 0 then 1 else count_matched towels
 
 let part1 (towels, patterns) =
-  List.map (count_matches memo towels) patterns
-  |> List.filter (( > ) 0)
+  List.map (Aoc.memoize memo (count_matches memo towels)) patterns
+  |> List.filter (( < ) 0)
   |> List.length
 
 let part2 (towels, patterns) =
-  List.map (memoize memo (count_matches memo towels)) patterns
+  List.map (Aoc.memoize memo (count_matches memo towels)) patterns
   |> List.fold_left ( + ) 0
 
 let _ =