Cleanup

aoc/src/dev/ctsk/aoc/days/Day11.scala

@@ -1,51 +1,40 @@
 package dev.ctsk.aoc.days
 
 import dev.ctsk.aoc._
-import scala.collection.mutable
+import scala.collection.mutable.{Map => MuMap}
 
 object Day11 extends Solver(11):
-  // upper and lower halves of number
-  def halves(n: Long): Option[(Long, Long)] =
+  private def halves(n: Long): Option[(Long, Long)] =
     val numDigits = (Math.log10(n) + 1).toLong
-    numDigits % 2 match
-      case 1 => None
-      case 0 => {
-        Some(
-          (
-            n % Math.pow(10, numDigits / 2).toLong,
-            n / Math.pow(10, numDigits / 2).toLong
-          )
-        )
-      }
+    if numDigits % 2 == 1 then None
+    else
+      val mod = Math.pow(10, numDigits / 2).toLong
+      Some(n % mod, n / mod)
 
-  def counter_compute(stones: Array[Long], depth: Long): Long =
-    var acc: mutable.Map[Long, Long] =
-      mutable.Map.from(stones.map((_, 1L)))
-
-    for (_ <- 0L until depth) {
-      val next = mutable.Map.empty[Long, Long].withDefaultValue(0L)
-      for ((stone, count) <- acc) {
+  private def count(initial: Seq[Long], depth: Int): Long =
+    def step(stones: MuMap[Long, Long]): MuMap[Long, Long] =
+      val next = MuMap.empty[Long, Long].withDefaultValue(0L)
+      for ((stone, count) <- stones) {
         if stone == 0 then next(1) += count
         else
-          halves(stone.toLong) match
+          halves(stone) match
             case Some((a, b)) =>
               next(a) += count
               next(b) += count
             case None =>
               next(stone * 2024) += count
       }
-      acc = next
-    }
+      next
 
-    acc.values.sum
+    val initMap = MuMap.from(initial.map((_, 1L)))
+    Seq.iterate(initMap, depth + 1)(step).last.values.sum
 
   def run(input: os.ReadablePath): (Timings, Solution) =
-    val in = longs(os.read.lines(input).head).toArray
-
-    val p1 = timed { counter_compute(in, 25) }
-    val p2 = timed { counter_compute(in, 75) }
+    val (pre_time, in) = timed { longs(os.read.lines(input).head) }
+    val (p1_time, p1_solution) = timed { count(in, 25) }
+    val (p2_time, p2_solution) = timed { count(in, 75) }
 
     (
-      Timings(0, p1._1, p2._1),
-      Solution(Long.box(p1._2), Long.box(p2._2))
+      Timings(pre_time, p1_time, p2_time),
+      Solution(Long.box(p1_solution), Long.box(p2_solution))
     )