2024 day 23 part 2

bin/day2423.ml

@@ -2,12 +2,8 @@ module StringMap = Map.Make (String)
 module StringSet = Set.Make (String)
 
 let[@warning "-32"] print_set set =
-  StringSet.iter
-    (fun x ->
-      print_string x;
-      print_char ' ')
-    set;
-  print_newline ()
+  StringSet.to_list set |> List.sort compare |> String.concat ","
+  |> Printf.printf "%s\n"
 
 let[@warning "-32"] print_sets = List.iter print_set
 
@@ -88,4 +84,35 @@ let part1 connections =
   print_sets rings;
   List.length rings
 
-let _ = Aoc.main load_file [ (string_of_int, part1) ]
+let rec search_candidate max_set connections current candidates =
+  match StringSet.choose_opt candidates with
+  | None ->
+      if StringSet.cardinal current > StringSet.cardinal max_set then current
+      else max_set
+  | Some h ->
+      let current' = StringSet.add h current in
+      let candidates' =
+        StringSet.inter candidates (StringMap.find h connections)
+      in
+      let max_set = search_candidate max_set connections current' candidates' in
+      search_candidate max_set connections current
+        (StringSet.remove h candidates)
+
+let find_max_set connections =
+  let rec impl max_set = function
+    | [] -> max_set
+    | (k, v) :: t ->
+        impl
+          (search_candidate max_set connections
+             (StringSet.add k StringSet.empty)
+             v)
+          t
+  in
+  impl StringSet.empty (StringMap.to_list connections)
+
+let part2 connections =
+  let max_set = find_max_set connections in
+  print_set max_set;
+  StringSet.cardinal max_set
+
+let _ = Aoc.main load_file [ (string_of_int, part1); (string_of_int, part2) ]