Day 14: Restroom Redoubt

README.md

@@ -18,4 +18,4 @@ Development occurs in language-specific directories:
 |[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)|[Day13.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day13.kt)|[day13.py](py/aoc2024/day13.py)||
-|[Day14.hs](hs/src/Day14.hs)||||
+|[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day14.kt)|||

kt/aoc2024-exe/src/commonBench/kotlin/com/github/ephemient/aoc2024/exe/Day14Bench.kt

@@ -0,0 +1,31 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day14
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Blackhole
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+
+@State(Scope.Benchmark)
+class Day14Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(14)
+    }
+
+    @Benchmark
+    fun part1() = Day14(input).part1()
+
+    @Benchmark
+    fun part2() = Day14(input).part2()
+
+    @Benchmark
+    fun solve(bh: Blackhole) {
+        val day14 = Day14(input)
+        bh.consume(day14.part1())
+        bh.consume(day14.part2())
+    }
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day14.kt

@@ -0,0 +1,47 @@
+package com.github.ephemient.aoc2024
+
+class Day14(input: String) {
+    private val robots = input.lineSequence().mapNotNull {
+        val (x, y, vx, vy) = pattern.matchEntire(it)?.destructured ?: return@mapNotNull null
+        Robot(x.toInt(), y.toInt(), vx.toInt(), vy.toInt())
+    }.toList()
+
+    fun part1(width: Int = WIDTH, height: Int = HEIGHT): Int {
+        val quadrants = IntArray(4)
+        for (robot in robots) {
+            val x = (robot.x + robot.vx * 100).mod(width)
+            val y = (robot.y + robot.vy * 100).mod(height)
+            quadrants[
+                (if (x < width / 2) 0 else if (x > width / 2) 1 else continue) or
+                    if (y < height / 2) 0 else if (y > height / 2) 2 else continue
+            ]++
+        }
+        println(quadrants.toList())
+        return quadrants.fold(1, Int::times)
+    }
+
+    fun part2() = (0..<WIDTH * HEIGHT).map { t ->
+        val positions = robots.mapTo(mutableSetOf()) { robot ->
+            (robot.x + robot.vx * t).mod(WIDTH) to (robot.y + robot.vy * t).mod(HEIGHT)
+        }.sortedWith(compareBy(IntPair::second, IntPair::first))
+        var consecutive = 1
+        var maxConsecutive = 0
+        for ((i, pos) in positions.withIndex()) {
+            if (pos.first + 1 to pos.second == positions.getOrNull(i + 1)) {
+                consecutive += 1
+            } else {
+                maxConsecutive = maxOf(consecutive, maxConsecutive)
+                consecutive = 1
+            }
+        }
+        t to maxConsecutive
+    }.maxBy(IntPair::second).also(::println).first
+
+    private data class Robot(val x: Int, val y: Int, val vx: Int, val vy: Int)
+
+    companion object {
+        private const val WIDTH = 101
+        private const val HEIGHT = 103
+        private val pattern = """p=(-?\d+),(-?\d+) v=(-?\d+),(-?\d+)""".toRegex()
+    }
+}

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

@@ -14,6 +14,7 @@ val days: List<Day> = listOf(
     Day(11, ::Day11, Day11::part1, Day11::part2),
     Day(12, ::Day12, Day12::part1, Day12::part2),
     Day(13, ::Day13, Day13::part1, Day13::part2),
+    Day(14, ::Day14, Day14::part1, Day14::part2),
 )
 
 data class Day(

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day14Test.kt

@@ -0,0 +1,29 @@
+package com.github.ephemient.aoc2024
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day14Test {
+    @Test
+    fun part1() {
+        assertEquals(12, Day14(example).part1(11, 7))
+    }
+
+    companion object {
+        val example =
+            """
+            |p=0,4 v=3,-3
+            |p=6,3 v=-1,-3
+            |p=10,3 v=-1,2
+            |p=2,0 v=2,-1
+            |p=0,0 v=1,3
+            |p=3,0 v=-2,-2
+            |p=7,6 v=-1,-3
+            |p=3,0 v=-1,-2
+            |p=9,3 v=2,3
+            |p=7,3 v=-1,2
+            |p=2,4 v=2,-3
+            |p=9,5 v=-3,-3
+            |""".trimMargin()
+    }
+}