Cleanup

aoc/src/dev/ctsk/aoc/Memo.scala

@@ -4,15 +4,8 @@ import scala.collection.mutable
 
 object Memo:
   def Y[I, O](f: (I, I => O) => O): I => O =
-    var yf: I => O = null
-    yf = Memo(f(_, yf(_)))
-    yf
+    lazy val yf: I => O = Memo(f(_, yf(_))); yf
 
 class Memo[-I, +O](f: I => O) extends (I => O):
   private[this] val memo = mutable.Map.empty[I, O]
-
-  def apply(i: I): O =
-    if memo.contains(i) then memo(i)
-    else {
-      val o = f(i); memo(i) = o; o
-    }
+  def apply(i: I): O = { lazy val o = f(i); memo.getOrElseUpdate(i, o) }

aoc/src/dev/ctsk/aoc/days/Day16.scala

@@ -51,7 +51,6 @@ object Day16 extends Solver(16):
       val all = mutable.Set(endPose)
       var cur = Set(endPose)
 
-      println(start)
       while cur.nonEmpty do
         cur = cur.filter(_ != Pose(start, Direction.Right)).flatMap(ancestor(_))
         all.addAll(cur)

aoc/src/dev/ctsk/aoc/days/Day19.scala

@@ -2,38 +2,23 @@ package dev.ctsk.aoc.days
 
 import dev.ctsk.aoc.*
 
-import scala.util.boundary
-import scala.util.boundary.break
-
 object Day19 extends Solver(19):
-
   def pre(input: os.ReadablePath): (Trie, Seq[String]) =
     val Array(rules_, words_) = os.read(input).split("\n\n")
     val trie = Trie()
     for rule <- rules_.split(", ") do trie.insert(rule)
     (trie, words_.linesIterator.toSeq)
 
-  def part1(trie: Trie, words: Seq[String]): Int =
-    def valid(word: String, inj: String => Boolean): Boolean =
-      if word.isEmpty then return true
-      boundary:
-        for p <- trie.prefixes(word) do
-          if inj(word.slice(p, word.length)) then break(true)
-        false
-
-    words.count(Memo.Y(valid))
-
-  def part2(trie: Trie, words: Seq[String]): Long =
-    def valid(word: String, inj: String => Long): Long =
-      if word.isEmpty then return 1L
-      trie.prefixes(word).map(p => inj(word.slice(p, word.length))).sum
-
-    words.map(Memo.Y(valid)).sum
+  private def arrangements(trie: Trie, word: String): Long =
+    def rec(offset: Int, inj: Int => Long): Long =
+      if offset == word.length then return 1L
+      trie.prefixes(word, offset).map(inj).sum
+    Memo.Y(rec)(0)
 
   override def run(input: os.ReadablePath): (Timings, Solution) =
     val (pre_time, (trie, words)) = timed { pre(input) }
-    val (p1_time, p1) = timed { part1(trie, words) }
-    val (p2_time, p2) = timed { part2(trie, words) }
+    val (p1_time, p1) = timed { words.count(arrangements(trie, _) > 0) }
+    val (p2_time, p2) = timed { words.map(arrangements(trie, _)).sum }
 
     (
       Timings(pre_time, p1_time, p2_time),