Day 10 2024 (#269)

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day10/Day10.kt

@@ -0,0 +1,69 @@
+package me.peckb.aoc._2024.calendar.day10
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+
+class Day10 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).read { lines ->
+    val (topoMap, trailHeads) = setup(lines)
+
+    fun dfs(location: Location) : Set<Location> {
+      val myElevation = topoMap[location.y][location.x]
+      if (myElevation == 9) return setOf(location)
+
+      return getNeighbors(location, topoMap).flatMap { dfs(it) }.toSet()
+    }
+
+    trailHeads.sumOf { dfs(it).size }
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).read { lines ->
+    val (topoMap, trailHeads) = setup(lines)
+
+    fun dfs(location: Location) : Int {
+      val myElevation = topoMap[location.y][location.x]
+      if (myElevation == 9) return 1
+
+      return getNeighbors(location, topoMap).sumOf { dfs(it) }
+    }
+
+    trailHeads.sumOf { dfs(it) }
+  }
+
+  private fun getNeighbors(location: Location, topoMap: MutableList<MutableList<Int>>) : List<Location> {
+    val (y, x) = location
+
+    val n = Location(y-1, x)
+    val e = Location(y, x+1)
+    val s = Location(y+1, x)
+    val w = Location(y, x-1)
+
+    val myElevation = topoMap[y][x]
+
+    return listOf(n, e, s, w)
+      .filter { it.y in topoMap.indices && it.x in topoMap[it.y].indices }
+      .filter { topoMap[it.y][it.x] == myElevation + 1 }
+  }
+
+  private fun setup(lines: Sequence<String>): Pair<MutableList<MutableList<Int>>, MutableList<Location>> {
+    val topoMap = mutableListOf<MutableList<Int>>()
+    val trailHeads = mutableListOf<Location>()
+
+    lines.forEachIndexed { yIndex, line ->
+      val row = mutableListOf<Int>()
+      line.forEachIndexed { xIndex, c ->
+        val elevation = c.digitToIntOrNull() ?: -1
+
+        if (elevation == 0) { trailHeads.add(Location(yIndex, xIndex)) }
+        row.add(elevation)
+      }
+      topoMap.add(row)
+    }
+
+    return topoMap to trailHeads
+  }
+}
+
+data class Location(val y: Int, val x: Int)

src/main/kotlin/me/peckb/aoc/_2024/calendar/day10/README.md

@@ -0,0 +1 @@
+## [Day 10: Hoof It](https://adventofcode.com/2024/day/10)

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

@@ -9,6 +9,7 @@ import me.peckb.aoc._2024.calendar.day06.Day06Test
 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 javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -26,4 +27,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day07Test: Day07Test)
   fun inject(day08Test: Day08Test)
   fun inject(day09Test: Day09Test)
+  fun inject(day10Test: Day10Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day10/Day10Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day10
+
+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 Day10Test {
+  @Inject
+  lateinit var day10: Day10
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay10PartOne() {
+    assertEquals(538, day10.partOne(DAY_10))
+  }
+
+  @Test
+  fun testDay10PartTwo() {
+    assertEquals(1110, day10.partTwo(DAY_10))
+  }
+
+  companion object {
+    private const val DAY_10: String = "advent-of-code-input/2024/day10.input"
+  }
+}