day 19

19/main.ml

@@ -0,0 +1,44 @@
+open Printf;;
+
+let rec list_of_lines in_file =
+  try
+    let line = input_line in_file in
+    line :: list_of_lines(in_file)
+  with End_of_file ->
+    close_in in_file;
+    []
+
+let get_input_lists list_of_lines =
+  match list_of_lines with
+  | towels_list :: _ :: tail -> (towels_list, tail)
+  | _ -> raise (Invalid_argument "Not enough lines")  
+  
+let rec try_any_towel cache towels pattern =
+  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
+      Hashtbl.add cache pattern result;
+      result
+
+let () =
+  let f = open_in "input.txt" in
+  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
+  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
+  printf "%d\n%d\n" result result2