2024-19 Scala 2

jurisk · Dec 19, 2024 · 28d60b0 · 28d60b0
1 parent 457cd7e
commit 28d60b0
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Showing 2 changed files with 34 additions and 14 deletions.
diff --git a/scala2/src/main/scala/jurisk/adventofcode/y2024/Advent19.scala b/scala2/src/main/scala/jurisk/adventofcode/y2024/Advent19.scala
@@ -1,14 +1,15 @@
 package jurisk.adventofcode.y2024
 
 import jurisk.utils.FileInput._
+import jurisk.utils.Memoize
 import jurisk.utils.Parsing.StringOps
 
 object Advent19 {
   final case class Input(
     stripes: List[String],
     towels: List[String],
   )
-  type N     = Int
+  type N     = Long
 
   def parse(input: String): Input = {
     val (stripes, towels) = input.split("\n\n").toList match {
@@ -18,22 +19,41 @@ object Advent19 {
     Input(stripes, towels)
   }
 
-  private def isValid(towel: String, stripes: List[String]): Boolean = {
-    if (towel.isEmpty) true
-    else {
-      stripes.exists { stripe =>
-//        println(s"Towel $towel, Stripe $stripe, Starts: ${towel.startsWith(stripe)}")
-        towel.startsWith(stripe) && isValid(towel.drop(stripe.length), stripes)
+  def part1(data: Input): N = {
+    def ways(towel: String, stripes: List[String]): N = {
+      if (towel.isEmpty) 1L
+      else {
+        stripes.map { stripe =>
+          if (towel.startsWith(stripe)) {
+            ways(towel.drop(stripe.length), stripes)
+          } else {
+            0L
+          }
+        }.sum
       }
     }
-  }
 
-  def part1(data: Input): N = {
-    data.towels.count(towel => isValid(towel, data.stripes))
+    data.towels.count(towel => ways(towel, data.stripes) > 0)
   }
 
-  def part2(data: Input): N =
-    0
+  def part2(data: Input): N = {
+    lazy val waysMemoized = Memoize.memoize1(ways)
+
+    def ways(towel: String): N = {
+      if (towel.isEmpty) 1L
+      else {
+        data.stripes.map { stripe =>
+          if (towel.startsWith(stripe)) {
+            waysMemoized(towel.drop(stripe.length))
+          } else {
+            0L
+          }
+        }.sum
+      }
+    }
+
+    data.towels.map(towel => waysMemoized(towel)).sum
+  }
 
   def parseFile(fileName: String): Input =
     parse(readFileText(fileName))

diff --git a/scala2/src/test/scala/jurisk/adventofcode/y2024/Advent19Spec.scala b/scala2/src/test/scala/jurisk/adventofcode/y2024/Advent19Spec.scala
@@ -20,11 +20,11 @@ class Advent19Spec extends AnyFreeSpec {
 
   "part 2" - {
     "test" in {
-      part2(testData) shouldEqual 0
+      part2(testData) shouldEqual 16
     }
 
     "real" in {
-      part2(realData) shouldEqual 0
+      part2(realData) shouldEqual 1100663950563322L
     }
   }
 }