Some effort to optimize day17

Day17.scala

@@ -50,7 +50,7 @@ case class State(x: Int, y: Int, dir: Dir):
   inline def left(using Seq[Int]) = next(Dir.fromOrdinal((dir.ordinal + 3) % 4))
   inline def right(using Seq[Int]) = next(Dir.fromOrdinal((dir.ordinal + 1) % 4))
 
-  def all(using Seq[Int]) = left ++ right
+  inline def all(using Seq[Int]) = left ++ right
 
 object Walk:
   // private val visited = mutable.Map.empty[State, Int]
@@ -62,8 +62,27 @@ object Walk:
     inline def +=(inline p: (State, Int)) = p match
       case (s, v) => arr(idx(s.x, s.y, s.dir)) = v
 
-  private val q =
+  // private val q =
-    mutable.PriorityQueue.empty[(Int, State)](using scala.math.Ordering.by((v, _) => -v))
+  //   mutable.PriorityQueue.empty[(Int, State)](using scala.math.Ordering.by((v, _) => -v))
+
+  private object q:
+    private inline val sz = 128
+    private val arrs = mutable.ArrayBuffer.fill(sz)(mutable.ArrayBuffer.empty[State])
+    private var ptr = 0
+    private var size = 0
+
+    def +=(p: (Int, State)): this.type =
+      val (d, s) = p
+      size += 1
+      arrs(d % sz).addOne(s)
+      this
+
+    inline def isEmpty = size == 0
+
+    inline def dequeue() =
+      size -= 1
+      while arrs(ptr % sz).isEmpty do ptr += 1
+      (ptr, arrs(ptr % sz).remove(arrs(ptr % sz).size - 1))
 
   def go()(using Seq[Int]): Option[Int] =
     Seq(Up, Down, Left, Right).foreach: dir =>