Day 14: Restroom Redoubt

README.md

@@ -11,7 +11,8 @@ Advent of Code is an Advent calendar of small programming puzzles by [Eric Wastl
 - Day 4: [Ceres Search](https://adventofcode.com/2024/day/4) -- [Day4.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day4.kt)
 - Day 5: [Print Queue](https://adventofcode.com/2024/day/5) -- [Day5.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day5.kt)
 - Day 7: [Bridge Repair](https://adventofcode.com/2024/day/7) -- [Day7.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day7.kt)
-- Day 8: [Resonant Collinearity](https://adventofcode.com/2024/day/8) -- [Day7.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day8.kt)
+- Day 8: [Resonant Collinearity](https://adventofcode.com/2024/day/8) -- [Day8.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day8.kt)
+- Day 14: [Restroom Redoubt](https://adventofcode.com/2024/day/14) -- [Day14.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day14.kt)
 
 ### Features
 

src/main/kotlin/days/Day14.kt

@@ -0,0 +1,69 @@
+package days
+
+@AdventOfCodePuzzle(
+    name = "Restroom Redoubt",
+    url = "https://adventofcode.com/2024/day/14",
+    date = Date(day = 14, year = 2024)
+)
+class Day14(val input: List<String>) : Puzzle {
+
+    val robots: List<Robot> = input.map { line -> Robot.from(line) }
+
+    val bounds = if (input.size < 100) Point(11, 7) else Point(101, 103)
+
+    override fun partOne() = robots
+        .map { it.move(100).bounds(bounds) }
+        .groupingBy() { quadrant(it.position) }.eachCount()
+        .filter { it.key != 0 }
+        .values
+        .fold(1L) { a, b -> a * b }
+
+    override fun partTwo(): Int =
+        generateSequence(0) { it + 1 }
+            .firstNotNullOfOrNull { seconds ->
+                val count = robots
+                    .map { it.move(seconds).bounds(bounds).position }
+                    .toSet().count()
+                if (count == input.size) seconds else null
+            } ?: error("No solution found")
+
+    fun draw(robots: List<Robot>) {
+        (0..bounds.y).forEach { y ->
+            (0..bounds.x).map { x ->
+                if (robots.any { it.position == Point(x, y) }) "#" else "."
+            }.joinToString("").also { println(it) }
+        }
+    }
+
+    private fun quadrant(p: Point): Int =
+        when {  // top left, top right, bottom left, bottom right
+            p.x in 0..<(bounds.x / 2) && p.y in 0..<(bounds.y / 2) -> 1      // top left
+            p.x in (bounds.x / 2 + 1)..bounds.x && p.y in 0..<(bounds.y / 2) -> 2    // top right
+            p.x in 0..<(bounds.x / 2) && p.y in (bounds.y / 2 + 1)..bounds.y -> 3     // bottom left
+            p.x in (bounds.x / 2 + 1)..bounds.x && p.y in (bounds.y / 2 + 1)..bounds.y -> 4     // bottom right
+            else -> 0
+        }
+
+    data class Robot(val position: Point, val velocity: Point) {
+        fun move(times: Int) = Robot(position + (velocity * times), velocity)
+        fun bounds(bounds: Point) = Robot(position.moveToBounds(bounds), velocity)
+
+        companion object {
+            fun from(line: String): Robot {
+                val (p, v) = line.split(" ")
+                val position = p.removePrefix("p=").split(",").map { it.toInt() }
+                val velocity = v.removePrefix("v=").split(",").map { it.toInt() }
+                return Robot(Point(position[0], position[1]), Point(velocity[0], velocity[1]))
+            }
+        }
+    }
+
+    data class Point(val x: Int, val y: Int) {
+        operator fun plus(other: Point) = Point(x + other.x, y + other.y)
+        operator fun minus(other: Point) = Point(x - other.x, y - other.y)
+        operator fun times(o: Int) = Point(x * o, y * o)
+
+        fun moveToBounds(bounds: Point) = Point(x.mod(bounds.x), y.mod(bounds.y))
+    }
+
+}