[2024/14] Restroom Redoubt (Part 2)

pfolta · Dec 14, 2024 · 43a846d · 43a846d
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diff --git a/README.md b/README.md
@@ -28,7 +28,7 @@
 |     2021 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |        |   ★    |   ★    |        |        |        |        |        |        |        |        |        |        |        |    26 |
 |     2022 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |        |        |        |        |        |        |        |   ☆    |        |        |        |   ☆    |    28 |
 |     2023 |   ★   |   ★   |   ★   |   ★   |   ☆   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    12 |
-|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |   ☆    |        |        |        |        |        |        |        |        |        |        |        |    27 |
+|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |   ★    |        |        |        |        |        |        |        |        |        |        |        |    28 |
 
 ## 🛷 How to run
 
@@ -177,7 +177,7 @@ e.g. `HandyHaversacks`)*
 |                                           |  11 | [Plutonian Pebbles](https://adventofcode.com/2024/day/11)                                              | [[Code](src/main/kotlin/adventofcode/year2024/Day11PlutonianPebbles.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day11PlutonianPebblesSpec.kt)]                                   | `194482`               | `232454623677743`                                |
 |                                           |  12 | [Garden Groups](https://adventofcode.com/2024/day/12)                                                  | [[Code](src/main/kotlin/adventofcode/year2024/Day12GardenGroups.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day12GardenGroupsSpec.kt)]                                           | `1573474`              | `966476`                                         |
 |                                           |  13 | [Claw Contraption](https://adventofcode.com/2024/day/13)                                               | [[Code](src/main/kotlin/adventofcode/year2024/Day13ClawContraption.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day13ClawContraptionSpec.kt)]                                     | `28138`                | `108394825772874`                                |
-|                                           |  14 | [Restroom Redoubt](https://adventofcode.com/2024/day/14)                                               | [[Code](src/main/kotlin/adventofcode/year2024/Day14RestroomRedoubt.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day14RestroomRedoubtSpec.kt)]                                     | `224357412`            |                                                  |
+|                                           |  14 | [Restroom Redoubt](https://adventofcode.com/2024/day/14)                                               | [[Code](src/main/kotlin/adventofcode/year2024/Day14RestroomRedoubt.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day14RestroomRedoubtSpec.kt)]                                     | `224357412`            | `7083`                                           |
 
 ## 🕯️ Useful commands
 

diff --git a/src/main/kotlin/adventofcode/year2024/Day14RestroomRedoubt.kt b/src/main/kotlin/adventofcode/year2024/Day14RestroomRedoubt.kt
@@ -32,6 +32,11 @@ class Day14RestroomRedoubt(customInput: PuzzleInput? = null) : Puzzle(customInpu
             .product()
     }
 
+    override fun partTwo() =
+        generateSequence(robots to 0) { (previous, seconds) -> previous.map(Robot::move) to seconds + 1 }
+            .first { (robots) -> robots.groupingBy(Robot::position).eachCount().all { (_, count) -> count == 1 } }
+            .second
+
     companion object {
         private val ROBOT_REGEX = """p=(\d+),(\d+) v=(-?\d+),(-?\d+)""".toRegex()
 
@@ -44,22 +49,8 @@ class Day14RestroomRedoubt(customInput: PuzzleInput? = null) : Puzzle(customInpu
             val velocity: Point2d,
         ) {
             fun move(): Robot {
-                val dx = position.x + velocity.x
-                val dy = position.y + velocity.y
-
-                val x =
-                    when {
-                        dx < 0 -> BATHROOM_WIDTH + dx
-                        dx >= BATHROOM_WIDTH -> dx - BATHROOM_WIDTH
-                        else -> dx
-                    }
-
-                val y =
-                    when {
-                        dy < 0 -> BATHROOM_HEIGHT + dy
-                        dy >= BATHROOM_HEIGHT -> dy - BATHROOM_HEIGHT
-                        else -> dy
-                    }
+                val x = (position.x + velocity.x).mod(BATHROOM_WIDTH)
+                val y = (position.y + velocity.y).mod(BATHROOM_HEIGHT)
 
                 return Robot(Point2d(x, y), velocity)
             }

diff --git a/src/test/kotlin/adventofcode/year2024/Day14RestroomRedoubtSpec.kt b/src/test/kotlin/adventofcode/year2024/Day14RestroomRedoubtSpec.kt
@@ -2,6 +2,6 @@ package adventofcode.year2024
 
 import adventofcode.PuzzleBaseSpec
 
-// The example for part 1 uses a different grid size than the actual input,
+// The example for part 1 uses a different grid size than the actual input and there is no example for part 2,
 // so this test runs the code on my actual input.
-class Day14RestroomRedoubtSpec : PuzzleBaseSpec(224357412)
+class Day14RestroomRedoubtSpec : PuzzleBaseSpec(224357412, 7083)