Day 11 2024

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day11/Day11.kt

@@ -0,0 +1,48 @@
+package me.peckb.aoc._2024.calendar.day11
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+
+class Day11 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).readOne { line ->
+    val stonesMap = createStonesMap(line)
+
+    repeat(25) { blink(stonesMap) }
+
+    stonesMap.entries.sumOf { it.value }
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).readOne { line ->
+    val stonesMap = createStonesMap(line)
+
+    repeat(75) { blink(stonesMap) }
+
+    stonesMap.entries.sumOf { it.value }
+  }
+
+  private fun createStonesMap(line: String) = mutableMapOf<Long, Long>().apply {
+    line.split(" ").forEach { merge(it.toLong(), 1, Long::plus) }
+  }
+
+  private fun blink(stones: MutableMap<Long, Long>) {
+    val entries = stones.entries.toList()
+
+    stones.clear()
+
+    entries.forEach { (stone, count) ->
+      if (stone == 0L) {
+        stones.merge(1, count, Long::plus)
+      } else if ("$stone".length % 2 == 0) {
+        val stoneStr = "$stone"
+        val half = stoneStr.length / 2
+
+        stones.merge(stoneStr.take(half).toLong(), count, Long::plus)
+        stones.merge(stoneStr.takeLast(half).toLong(), count, Long::plus)
+      } else {
+        stones.merge(stone * 2024, count, Long::plus)
+      }
+    }
+  }
+}

src/main/kotlin/me/peckb/aoc/_2024/calendar/day11/README.md

@@ -0,0 +1 @@
+## [Day 11: Plutonian Pebbles](https://adventofcode.com/2024/day/11)

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

@@ -10,6 +10,7 @@ import me.peckb.aoc._2024.calendar.day07.Day07Test
 import me.peckb.aoc._2024.calendar.day08.Day08Test
 import me.peckb.aoc._2024.calendar.day09.Day09Test
 import me.peckb.aoc._2024.calendar.day10.Day10Test
+import me.peckb.aoc._2024.calendar.day11.Day11Test
 import javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -28,4 +29,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day08Test: Day08Test)
   fun inject(day09Test: Day09Test)
   fun inject(day10Test: Day10Test)
+  fun inject(day11Test: Day11Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day11/Day11Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day11
+
+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 Day11Test {
+  @Inject
+  lateinit var day11: Day11
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay11PartOne() {
+    assertEquals(185205, day11.partOne(DAY_11))
+  }
+
+  @Test
+  fun testDay11PartTwo() {
+    assertEquals(221280540398419, day11.partTwo(DAY_11))
+  }
+
+  companion object {
+    private const val DAY_11: String = "advent-of-code-input/2024/day11.input"
+  }
+}