Day 07 2024 (#266)

* Day 07 2024

Author: peckb1

src/main/kotlin/me/peckb/aoc/_2024/calendar/day07/Day07.kt

@@ -0,0 +1,49 @@
+package me.peckb.aoc._2024.calendar.day07
+
+import javax.inject.Inject
+import me.peckb.aoc.generators.InputGenerator.InputGeneratorFactory
+
+class Day07 @Inject constructor(
+  private val generatorFactory: InputGeneratorFactory,
+) {
+  fun partOne(filename: String) = generatorFactory.forFile(filename).readAs(::calibration) { input ->
+    input.filter { check(it, listOf(ADD, MULTIPLY)) }.sumOf { it.value }
+  }
+
+  fun partTwo(filename: String) = generatorFactory.forFile(filename).readAs(::calibration) { input ->
+    input.filter { check(it, listOf(ADD, MULTIPLY, CONCAT)) }.sumOf { it.value }
+  }
+
+  fun check(calibration: Calibration, operands: List<Operand>): Boolean {
+    val (n, m) = calibration.numbers.take(2)
+    val otherNumbers = calibration.numbers.drop(2)
+    return operands.any { op -> check(calibration.value, listOf(op.invoke(n, m)).plus(otherNumbers), operands) }
+  }
+
+  fun check(targetVal: Long, remainingNumbers: List<Long>, operands: List<Operand>) : Boolean {
+    if (remainingNumbers.isEmpty())      return false
+    if (remainingNumbers.size == 1)      return targetVal == remainingNumbers[0]
+    if (remainingNumbers[0] > targetVal) return false
+
+    val (n, m) = remainingNumbers.take(2)
+    val otherNumbers = remainingNumbers.drop(2)
+    return operands.any { op -> check(targetVal, listOf(op.invoke(n, m)).plus(otherNumbers), operands) }
+  }
+
+  private fun calibration(line: String): Calibration {
+    return line.split(": ").let { (valueStr, numbersStr) ->
+      val numbers = numbersStr.split(" ").map(String::toLong)
+      Calibration(valueStr.toLong(), numbers)
+    }
+  }
+
+  companion object {
+    val ADD      = { n: Long, m: Long -> n + m }
+    val MULTIPLY = { n: Long, m: Long -> n * m }
+    val CONCAT   = { n: Long, m: Long -> "$n$m".toLong() }
+  }
+}
+
+typealias Operand = (Long, Long) -> Long
+
+data class Calibration(val value: Long, val numbers: List<Long>)

src/main/kotlin/me/peckb/aoc/_2024/calendar/day07/README.md

@@ -0,0 +1 @@
+## [Day 7: Bridge Repair](https://adventofcode.com/2024/day/7)

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

@@ -6,6 +6,7 @@ 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 me.peckb.aoc._2024.calendar.day06.Day06Test
+import me.peckb.aoc._2024.calendar.day07.Day07Test
 import javax.inject.Singleton
 import me.peckb.aoc.DayComponent
 import me.peckb.aoc.InputModule
@@ -20,4 +21,5 @@ internal interface TestDayComponent : DayComponent {
   fun inject(day04Test: Day04Test)
   fun inject(day05Test: Day05Test)
   fun inject(day06Test: Day06Test)
+  fun inject(day07Test: Day07Test)
 }

src/test/kotlin/me/peckb/aoc/_2024/calendar/day07/Day07Test.kt

@@ -0,0 +1,32 @@
+package me.peckb.aoc._2024.calendar.day07
+
+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 Day07Test {
+  @Inject
+  lateinit var day07: Day07
+
+  @BeforeEach
+  fun setup() {
+    DaggerTestDayComponent.create().inject(this)
+  }
+
+  @Test
+  fun testDay07PartOne() {
+    assertEquals(6231007345478, day07.partOne(DAY_07))
+  }
+
+  @Test
+  fun testDay07PartTwo() {
+    assertEquals(333027885676693, day07.partTwo(DAY_07))
+  }
+
+  companion object {
+    private const val DAY_07: String = "advent-of-code-input/2024/day07.input"
+  }
+}