Day 13: Claw Contraption

README.md

@@ -17,4 +17,4 @@ Development occurs in language-specific directories:
 |[Day10.hs](hs/src/Day10.hs)|[Day10.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day10.kt)|[day10.py](py/aoc2024/day10.py)|[day10.rs](rs/src/day10.rs)|
 |[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)|[day11.rs](rs/src/day11.rs)|
 |[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt)|[day12.py](py/aoc2024/day12.py)||
-|[Day13.hs](hs/src/Day13.hs)||||
+|[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt)|||

kt/aoc2024-exe/src/commonBench/kotlin/com/github/ephemient/aoc2024/exe/Day13Bench.kt

@@ -0,0 +1,31 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day13
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Blackhole
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+
+@State(Scope.Benchmark)
+class Day13Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(13)
+    }
+
+    @Benchmark
+    fun part1() = Day13(input).part1()
+
+    @Benchmark
+    fun part2() = Day13(input).part2()
+
+    @Benchmark
+    fun solve(bh: Blackhole) {
+        val day13 = Day13(input)
+        bh.consume(day13.part1())
+        bh.consume(day13.part2())
+    }
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day13.kt

@@ -0,0 +1,42 @@
+package com.github.ephemient.aoc2024
+
+class Day13(input: String) {
+    private val machines = pattern.findAll(input).map { matchResult ->
+        val (ax, ay, bx, `by`, x, y) = matchResult.destructured
+        Machine(ax.toLong(), ay.toLong(), bx.toLong(), `by`.toLong(), x.toLong(), y.toLong())
+    }.toList()
+
+    fun part1() = machines.sumOf { it.solve() }
+
+    fun part2() = machines.sumOf { it.copy(x = it.x + 10000000000000, y = it.y + 10000000000000).solve() }
+
+    private data class Machine(
+        val ax: Long,
+        val ay: Long,
+        val bx: Long,
+        val `by`: Long,
+        val x: Long,
+        val y: Long,
+    ) {
+        fun solve(): Long {
+            val aNumerator = x * `by` - y * bx
+            val aDenominator = ax * `by` - bx * ay
+            val bNumerator = x * ay - y * ax
+            val bDenominator = ay * bx - `by` * ax
+            return if (aNumerator % aDenominator == 0L && bNumerator % bDenominator == 0L) {
+                val a = aNumerator / aDenominator
+                val b = bNumerator / bDenominator
+                3 * a + b
+            } else 0
+        }
+    }
+
+    companion object {
+        private val pattern =
+            """
+            Button A: X\+(\d+), Y\+(\d+)
+            Button B: X\+(\d+), Y\+(\d+)
+            Prize: X=(\d+), Y=(\d+)
+            """.trimIndent().toRegex()
+    }
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Days.kt

@@ -13,6 +13,7 @@ val days: List<Day> = listOf(
     Day(10, ::Day10, Day10::part1, Day10::part2),
     Day(11, ::Day11, Day11::part1, Day11::part2),
     Day(12, ::Day12, Day12::part1, Day12::part2),
+    Day(13, ::Day13, Day13::part1, Day13::part2),
 )
 
 data class Day(

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day13Test.kt

@@ -0,0 +1,32 @@
+package com.github.ephemient.aoc2024
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day13Test {
+    @Test
+    fun part1() {
+        assertEquals(480, Day13(example).part1())
+    }
+
+    companion object {
+        val example =
+            """
+            |Button A: X+94, Y+34
+            |Button B: X+22, Y+67
+            |Prize: X=8400, Y=5400
+            |
+            |Button A: X+26, Y+66
+            |Button B: X+67, Y+21
+            |Prize: X=12748, Y=12176
+            |
+            |Button A: X+17, Y+86
+            |Button B: X+84, Y+37
+            |Prize: X=7870, Y=6450
+            |
+            |Button A: X+69, Y+23
+            |Button B: X+27, Y+71
+            |Prize: X=18641, Y=10279
+            |""".trimMargin()
+    }
+}