2020 day23 (#224)

* Initial commit, needs cleanup

* cleanup

* remove notion of counterclockwise link

src/main/kotlin/me/peckb/aoc/_2020/calendar/day23/Day23.kt

@@ -0,0 +1,122 @@
+package me.peckb.aoc._2020.calendar.day23
+
+import javax.inject.Inject
+
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+import java.lang.StringBuilder
+
+class Day23 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).readOne { cupLabeling ->
+    val cups = mutableMapOf<Int, Cup>()
+    var currentCup: Cup? = null
+    var lastCup: Cup? = null
+
+    cupLabeling.forEach { cupCodeChar ->
+      val id = Character.getNumericValue(cupCodeChar)
+      Cup(id).also { newCup ->
+        cups[id] = newCup
+        if (currentCup == null) { currentCup = newCup }
+        lastCup?.also {
+          it.clockwiseCup = newCup
+        }
+        lastCup = newCup
+      }
+    }
+
+    lastCup?.also { it.clockwiseCup = currentCup!! }
+
+    cups.runGame(100, currentCup!!)
+
+    cupOrder(cups).drop(1).dropLast(1)
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).readOne { cupLabeling ->
+    val cups = mutableMapOf<Int, Cup>()
+    var currentCup: Cup? = null
+    var lastCup: Cup? = null
+
+    fun setupNewCup (id: Int) {
+      Cup(id).also { newCup ->
+        cups[id] = newCup
+        if (currentCup == null) { currentCup = newCup }
+        lastCup?.also {
+          it.clockwiseCup = newCup
+        }
+        lastCup = newCup
+      }
+    }
+
+    cupLabeling.forEach { cupCodeChar -> setupNewCup(Character.getNumericValue(cupCodeChar)) }
+    lastCup?.also { it.clockwiseCup = currentCup!! }
+
+    val previousMaxCup = cups.keys.maxOrNull()!!
+
+    repeat(1_000_000 - previousMaxCup) { setupNewCup(previousMaxCup + it + 1) }
+    lastCup?.also { it.clockwiseCup = currentCup!! }
+
+    cups.runGame(10_000_000, currentCup!!)
+
+    cups[1]?.clockwiseCup?.id!!.toLong() * cups[1]?.clockwiseCup?.clockwiseCup?.id!!.toLong()
+  }
+
+  private fun Map<Int, Cup>.runGame(rounds: Int, startCup: Cup) {
+
+    val allCupIds = keys
+    val maxCupId = allCupIds.maxOrNull()!!
+    val minCupId = allCupIds.minOrNull()!!
+
+    var currentCup = startCup
+
+    repeat(rounds) { round ->
+      // pick up the next three cups
+      val firstCupToPickup = currentCup.clockwiseCup
+      val secondCupToPickup = firstCupToPickup.clockwiseCup
+      val thirdCupToPickup   = secondCupToPickup.clockwiseCup
+
+      val cupsInHand = setOfNotNull(firstCupToPickup.id, secondCupToPickup.id, thirdCupToPickup.id)
+      var destinationCupId = currentCup.id
+      do {
+        destinationCupId -= 1
+        if (destinationCupId < minCupId) destinationCupId = maxCupId
+      } while(cupsInHand.contains(destinationCupId))
+
+      val destinationCup = this[destinationCupId]!!
+
+      // from:
+      //   q -> C -> [a, b, c] -> r
+      //   x -> D -> y
+      val r = thirdCupToPickup.clockwiseCup
+      val y = destinationCup.clockwiseCup
+      // to:
+      //   q -> C -> r
+      //   x -> D -> [a, b, c] -> y
+      currentCup.clockwiseCup = r
+      destinationCup.clockwiseCup = firstCupToPickup
+      thirdCupToPickup.clockwiseCup = y
+
+      currentCup = currentCup.clockwiseCup
+    }
+  }
+
+  private fun cupOrder(cups: MutableMap<Int, Cup>): String {
+    var cup = cups[1]!!
+    val sb = StringBuilder().apply {
+      append(cup.id)
+    }
+    repeat(cups.size) {
+      sb.append("${cup.clockwiseCup.id}")
+      cup = cup.clockwiseCup
+    }
+    return sb.toString()
+  }
+
+  data class Cup(val id: Int) {
+    lateinit var clockwiseCup: Cup
+
+    override fun toString(): String {
+      return id.toString()
+    }
+  }
+}

src/main/kotlin/me/peckb/aoc/_2020/calendar/day23/README.md

@@ -0,0 +1 @@
+## [Day 23: Crab Cups](https://adventofcode.com/2020/day/23)

src/test/kotlin/me/peckb/aoc/_2020/TestDayComponent.kt

@@ -22,6 +22,7 @@ import me.peckb.aoc._2020.calendar.day19.Day19Test
 import me.peckb.aoc._2020.calendar.day20.Day20Test
 import me.peckb.aoc._2020.calendar.day21.Day21Test
 import me.peckb.aoc._2020.calendar.day22.Day22Test
+import me.peckb.aoc._2020.calendar.day23.Day23Test
 import javax.inject.Singleton
 
 import me.peckb.aoc.DayComponent
@@ -53,4 +54,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day20Test: Day20Test)
   fun inject(day21Test: Day21Test)
   fun inject(day22Test: Day22Test)
+  fun inject(day23Test: Day23Test)
 }

src/test/kotlin/me/peckb/aoc/_2020/calendar/day23/Day23Test.kt

@@ -0,0 +1,33 @@
+package me.peckb.aoc._2020.calendar.day23
+
+import javax.inject.Inject
+
+
+import me.peckb.aoc._2020.DaggerTestDayComponent
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+internal class Day23Test {
+  @Inject
+  lateinit var day23: Day23
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay23PartOne() {
+    assertEquals("54327968", day23.partOne(DAY_23))
+  }
+
+  @Test
+  fun testDay23PartTwo() {
+    assertEquals(157410423276, day23.partTwo(DAY_23))
+  }
+
+  companion object {
+    private const val DAY_23: String = "advent-of-code-input/2020/day23.input"
+  }
+}