Day 17 2024 (#279)

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day17/Day17.kt

@@ -0,0 +1,83 @@
+package me.peckb.aoc._2024.calendar.day17
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+import kotlin.math.pow
+
+class Day17 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val computer = Computer.fromInput(input)
+    val output = runProgram(computer)
+    output.joinToString(",")
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).read { input ->
+    val computer = Computer.fromInput(input)
+
+    findProgram(computer, computer.operations.map{ it.toLong() })
+  }
+
+  private fun findProgram(computer: Computer, target: List<Long>): Long {
+    var aStart = if (target.size > 1) {
+      8 * findProgram(computer, target.drop(1))
+    } else { 0 }
+
+    while(runProgram(computer.copy(aReg = aStart)) != target) {
+      aStart++
+    }
+
+    return aStart
+  }
+
+  private fun runProgram(c: Computer): List<Long> {
+    val output = mutableListOf<Long>()
+    var programPointer = 0
+
+    while(programPointer < c.operations.size - 1) {
+      val opcode  = c.operations[programPointer]
+      val operand = c.operations[programPointer + 1]
+
+      programPointer += 2
+
+      val comboOperand by lazy {
+        when (operand) {
+          0, 1, 2, 3 -> operand.toLong()
+          4 -> c.aReg
+          5 -> c.bReg
+          6 -> c.cReg
+          else -> throw IllegalArgumentException("Invalid operand: $operand")
+        }
+      }
+
+      when (opcode) {
+        0 -> c.aReg = (c.aReg / 2.0.pow(comboOperand.toDouble())).toLong()
+        1 -> c.bReg = c.bReg xor operand.toLong()
+        2 -> c.bReg = comboOperand % 8
+        3 -> if (c.aReg != 0L) { programPointer = operand }
+        4 -> c.bReg = c.bReg xor c.cReg
+        5 -> output.add(comboOperand % 8)
+        6 -> c.bReg = (c.aReg / 2.0.pow(comboOperand.toDouble())).toLong()
+        7 -> c.cReg = (c.aReg / 2.0.pow(comboOperand.toDouble())).toLong()
+      }
+    }
+
+    return output
+  }
+}
+
+data class Computer(var aReg: Long, var bReg: Long, var cReg: Long, val operations: List<Int>) {
+  companion object {
+    fun fromInput(input: Sequence<String>): Computer {
+      val data = input.toList()
+      val aReg = data[0].split("A: ")[1].toLong()
+      val bReg = data[1].split("B: ")[1].toLong()
+      val cReg = data[2].split("C: ")[1].toLong()
+
+      val program = data[4].split(": ")[1].split(",").map { it.toInt() }
+
+      return Computer(aReg, bReg, cReg, program)
+    }
+  }
+}

src/main/kotlin/me/peckb/aoc/_2024/calendar/day17/README.md

@@ -0,0 +1 @@
+## [Day 17: Chronospatial Computer](https://adventofcode.com/2024/day/17)

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

@@ -16,6 +16,7 @@ import me.peckb.aoc._2024.calendar.day13.Day13Test
 import me.peckb.aoc._2024.calendar.day14.Day14Test
 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 javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -40,4 +41,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day14Test: Day14Test)
   fun inject(day15Test: Day15Test)
   fun inject(day16Test: Day16Test)
+  fun inject(day17Test: Day17Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day17/Day17Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day17
+
+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 Day17Test {
+  @Inject
+  lateinit var day17: Day17
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay17PartOne() {
+    assertEquals("2,7,6,5,6,0,2,3,1", day17.partOne(DAY_17))
+  }
+
+  @Test
+  fun testDay17PartTwo() {
+    assertEquals(107_416_870_455_451, day17.partTwo(DAY_17))
+  }
+
+  companion object {
+    private const val DAY_17: String = "advent-of-code-input/2024/day17.input"
+  }
+}