Day 10 2025 (#305)

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2025/calendar/day10/Day10.kt

@@ -0,0 +1,125 @@
+package me.peckb.aoc._2025.calendar.day10
+
+import com.microsoft.z3.ArithExpr
+import com.microsoft.z3.Context
+import com.microsoft.z3.IntExpr
+import com.microsoft.z3.IntNum
+import com.microsoft.z3.IntSort
+import com.microsoft.z3.Status
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+import kotlin.collections.component1
+import kotlin.collections.component2
+import kotlin.math.min
+
+class Day10 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).readAs(::day10) { input ->
+    input.sumOf { machine -> flipLights(machine.indicatorLights, machine.buttonSchematics) }
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).readAs(::day10) { input ->
+    input.sumOf { machine -> enableJoltages(machine) }
+  }
+
+  private fun enableJoltages(machine: Machine) : Int {
+    return Context().use { ctx ->
+      val opt = ctx.mkOptimize()
+
+      fun intVariableOf(name: String) = ctx.mkIntConst(name)
+
+      fun intValueOf(value: Int) = ctx.mkInt(value)
+
+      infix fun IntExpr.gte(t: IntExpr) = ctx.mkGe(this, t)
+
+      operator fun ArithExpr<IntSort>.plus(t: IntExpr) = ctx.mkAdd(this, t)
+
+      infix fun ArithExpr<IntSort>.equalTo(t: IntExpr) = ctx.mkEq(this, t)
+
+      fun List<IntExpr>.sum() = ctx.mkAdd(*this.toTypedArray())
+
+      val ZERO = intValueOf(0)
+
+      val affectedJoltages = mutableMapOf<Int, MutableList<IntExpr>>()
+      val buttonVariables = machine.buttonSchematics.mapIndexed { index, schematic ->
+        // create button variable
+        intVariableOf(index.toString()).also { buttonVariable ->
+          // track the joltages if affects
+          schematic.affectedIndices.forEach { affectedIndex ->
+            affectedJoltages.computeIfAbsent(affectedIndex) { _ -> mutableListOf() }.add(buttonVariable)
+          }
+          // add it to the optimizer
+          opt.Add(buttonVariable gte ZERO)
+        }
+      }
+
+      affectedJoltages.forEach { (joltageIndex, buttonsAffecting) ->
+        val targetValue = intValueOf(machine.joltages[joltageIndex])
+        val sumOfButtonPresses = buttonsAffecting.sum()
+        opt.Add(sumOfButtonPresses equalTo targetValue)
+      }
+
+      opt.MkMinimize(buttonVariables.sum())
+
+      val status = opt.Check()
+
+      if (status == Status.SATISFIABLE) {
+        val model = opt.getModel()
+        ((model.evaluate(buttonVariables.sum(), true) as IntNum).int)
+      } else {
+        throw IllegalStateException("No Solution Found")
+      }
+    }
+  }
+
+  fun flipLights(goal: String, buttonSchematics: List<ButtonSchematic>): Long {
+    val minPressesForState = mutableMapOf(".".repeat(goal.length) to 0L)
+    while(!minPressesForState.containsKey(goal)) {
+      minPressesForState.entries.toList().forEach { (light, cost) ->
+        val nextStates = possibleLights(light, buttonSchematics)
+        nextStates.forEach { state ->
+          if (minPressesForState.containsKey(state)) {
+            minPressesForState[state] = min(minPressesForState[state]!!, cost + 1)
+          } else {
+            minPressesForState[state] = cost + 1
+          }
+        }
+      }
+    }
+
+    return minPressesForState[goal]!!
+  }
+
+  fun possibleLights(current: String, buttonSchematics: List<ButtonSchematic>): List<String> {
+    return buttonSchematics.map { applyLightPress(current, it) }
+  }
+
+  private fun applyLightPress(current: String, buttonSchematic: ButtonSchematic): String {
+    return current.mapIndexed { index, c ->
+      if (buttonSchematic.affectedIndices.contains(index)) {
+        if (c == '#') { '.' } else { '#' }
+      } else { c }
+    }.joinToString("")
+  }
+
+  private fun day10(line: String): Machine {
+    // SAMPLE: [.##.] (3) (1,3) (2) (2,3) (0,2) (0,1) {3,5,4,7}
+    val indicatorLights = line.substringBefore(']').drop(1)
+    val buttonSchematics = line.substringAfter("] ").substringBefore(" {").split(" ").map { buttonList ->
+      val buttonIndices = buttonList.drop(1).dropLast(1).split(",").map { it.toInt() }
+      ButtonSchematic(buttonIndices)
+    }
+    val joltages = line.substringAfter('{').dropLast(1).split(",").map { it.toInt() }
+
+    return Machine(indicatorLights, buttonSchematics, joltages)
+  }
+}
+
+data class Machine(
+  val indicatorLights: String,
+  val buttonSchematics: List<ButtonSchematic>,
+  val joltages: List<Int>,
+)
+
+data class ButtonSchematic(val affectedIndices: List<Int>)

src/main/kotlin/me/peckb/aoc/_2025/calendar/day10/README.md

@@ -0,0 +1 @@
+## [Day 10: Factory](https://adventofcode.com/2025/day/10)

src/test/kotlin/me/peckb/aoc/_2025/TestDayComponent.kt

@@ -9,6 +9,7 @@ import me.peckb.aoc._2025.calendar.day06.Day06Test
 import me.peckb.aoc._2025.calendar.day07.Day07Test
 import me.peckb.aoc._2025.calendar.day08.Day08Test
 import me.peckb.aoc._2025.calendar.day09.Day09Test
+import me.peckb.aoc._2025.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/_2025/calendar/day10/Day10Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2025.calendar.day10
+
+import javax.inject.Inject
+
+import me.peckb.aoc._2025.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(527, day10.partOne(DAY_10))
+  }
+
+  @Test
+  fun testDay10PartTwo() {
+    assertEquals(19810, day10.partTwo(DAY_10))
+  }
+
+  companion object {
+    private const val DAY_10: String = "advent-of-code-input/2025/day10.input"
+  }
+}