Simplify

lib/year2023/day25.ml

@@ -40,17 +40,12 @@ let make_graph lines =
 ;;
 
 let solve graph =
- let rec aux (nodes, edges) =
- let ln = Set.length nodes in
- let le = List.length edges in
- if ln = 2
- then
- if le = 3
- then
- Some (Set.fold nodes ~init:1 ~f:(fun acc node -> acc * (String.length node / 3)))
- else None
- else (
- let n = Random.int le in
+ let rec aux = function
+ | nodes, edges when Set.length nodes = 2 && List.length edges = 3 ->
+ Some (Set.fold nodes ~init:1 ~f:(fun acc node -> acc * (String.length node / 3)))
+ | nodes, _ when Set.length nodes = 2 -> None
+ | nodes, edges ->
+ let n = edges |> List.length |> Random.int in
  let a, b = List.nth_exn edges n in
  let ab = a ^ b in
  let edges' =
@@ -61,7 +56,7 @@ let solve graph =
  | e -> Some e)
  in
  let nodes' = Set.add (Set.remove (Set.remove nodes a) b) ab in
- aux (nodes', edges'))
+ aux (nodes', edges')
  in
  Util.Sequence.nats |> Sequence.find_map ~f:(fun _ -> aux graph) |> Option.value_exn
 ;;