Day 19 2024 (#282)

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day19/Day19.kt

@@ -0,0 +1,47 @@
+package me.peckb.aoc._2024.calendar.day19
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+
+class Day19 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val data = input.toList()
+    val availableTowelTypes = data.first().split(", ")
+
+    data.drop(2).count { pattern -> isPossible(pattern, availableTowelTypes) }
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val data = input.toList()
+    val availableTowelTypes = data.first().split(", ")
+
+    data.drop(2).sumOf { pattern -> isPossibleCount(pattern, availableTowelTypes) }
+  }
+
+  private fun isPossible(pattern: String, availableTowelTypes: List<String>): Boolean {
+    if (pattern.isEmpty()) return true
+    if (found[pattern] == false) return false
+
+    return availableTowelTypes.any { towel ->
+      pattern.startsWith(towel) && isPossible(pattern.substring(towel.length), availableTowelTypes)
+    }.also { found[pattern] = it }
+  }
+
+  private fun isPossibleCount(pattern: String, availableTowelTypes: List<String>): Long {
+    if (pattern.isEmpty()) return 1
+    foundCount[pattern]?.let { return it }
+
+    return availableTowelTypes.sumOf { towel ->
+      if (!pattern.startsWith(towel)) { 0L } else {
+        isPossibleCount(pattern.substring(towel.length), availableTowelTypes)
+      }
+    }.also { foundCount[pattern] = it }
+  }
+
+  companion object {
+    val found = mutableMapOf<String, Boolean>()
+    val foundCount = mutableMapOf<String, Long>()
+  }
+}

src/main/kotlin/me/peckb/aoc/_2024/calendar/day19/README.md

@@ -0,0 +1 @@
+## [Day 19: Linen Layout](https://adventofcode.com/2024/day/19)

src/test/kotlin/me/peckb/aoc/_2024/TestDayComponent.kt

@@ -18,6 +18,7 @@ import me.peckb.aoc._2024.calendar.day15.Day15Test
 import me.peckb.aoc._2024.calendar.day16.Day16Test
 import me.peckb.aoc._2024.calendar.day17.Day17Test
 import me.peckb.aoc._2024.calendar.day18.Day18Test
+import me.peckb.aoc._2024.calendar.day19.Day19Test
 import javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -44,4 +45,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day16Test: Day16Test)
   fun inject(day17Test: Day17Test)
   fun inject(day18Test: Day18Test)
+  fun inject(day19Test: Day19Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day19/Day19Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day19
+
+import javax.inject.Inject
+
+import me.peckb.aoc._2024.DaggerTestDayComponent
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+internal class Day19Test {
+  @Inject
+  lateinit var day19: Day19
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay19PartOne() {
+    assertEquals(255, day19.partOne(DAY_19))
+  }
+
+  @Test
+  fun testDay19PartTwo() {
+    assertEquals(621820080273474, day19.partTwo(DAY_19))
+  }
+
+  companion object {
+    private const val DAY_19: String = "advent-of-code-input/2024/day19.input"
+  }
+}