Day 05 2024 (#263)

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day05/Day05.kt

@@ -0,0 +1,59 @@
+package me.peckb.aoc._2024.calendar.day05
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+
+class Day05 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val (rules, updates) = input.parseInput()
+    val (validUpdates, _) = validate(rules, updates)
+
+    sumMiddlePages(validUpdates)
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val (rules, updates) = input.parseInput()
+    val (_, invalidUpdates) = validate(rules, updates)
+
+    sumMiddlePages(invalidUpdates.map { it.reSort(rules) })
+  }
+
+  private fun Sequence<String>.parseInput(): Pair<Map<Rule, Unit>, List<Update>> {
+    val rules = mutableMapOf<Rule, Unit>()
+    val updates = mutableListOf<Update>()
+
+    var readingRules = true
+    this.forEach { line ->
+      if (line.isBlank()) { readingRules = false }
+      else {
+        if (readingRules) {
+          rules[line.split("|").map { it.toInt() }.let{ (b, a) -> Rule(b, a) }] = Unit
+        } else {
+          updates.add(Update(line.split(",").map { it.toInt() }))
+        }
+      }
+    }
+
+    return rules to updates
+  }
+
+  private fun validate(rules: Map<Rule, Unit>, updates: List<Update>): Pair<List<Update>, List<Update>> {
+    return updates.partition { update ->
+      update.pages.windowed(2).all { (before, after) ->
+        rules.containsKey(Rule(before, after))
+      }
+    }
+  }
+
+  private fun sumMiddlePages(updates: List<Update>) = updates.sumOf { it.pages[(it.pages.size / 2)] }
+}
+
+data class Rule(val before: Int, val after: Int)
+
+data class Update(val pages: List<Int>) {
+  fun reSort(rules: Map<Rule, Unit>) = pages.sortedWith { before, after ->
+    if (rules.containsKey(Rule(before, after))) -1 else 1
+  }.let(::Update)
+}

src/main/kotlin/me/peckb/aoc/_2024/calendar/day05/README.md

@@ -0,0 +1 @@
+## [Day 5: Print Queue](https://adventofcode.com/2024/day/5)

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

@@ -4,6 +4,7 @@ import dagger.Component
 import me.peckb.aoc._2024.calendar.day02.Day02Test
 import me.peckb.aoc._2024.calendar.day03.Day03Test
 import me.peckb.aoc._2024.calendar.day04.Day04Test
+import me.peckb.aoc._2024.calendar.day05.Day05Test
 import javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -16,4 +17,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day02Test: Day02Test)
   fun inject(day03Test: Day03Test)
   fun inject(day04Test: Day04Test)
+  fun inject(day05Test: Day05Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day05/Day05Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day05
+
+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 Day05Test {
+  @Inject
+  lateinit var day05: Day05
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay05PartOne() {
+    assertEquals(5129, day05.partOne(DAY_05))
+  }
+
+  @Test
+  fun testDay05PartTwo() {
+    assertEquals(4077, day05.partTwo(DAY_05))
+  }
+
+  companion object {
+    private const val DAY_05: String = "advent-of-code-input/2024/day05.input"
+  }
+}