Solve 2024 day 14 part 2

sim642 · Dec 14, 2024 · fcb53f4 · fcb53f4
1 parent 0f5e379
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diff --git a/src/main/scala/eu/sim642/adventofcode2024/Day14.scala b/src/main/scala/eu/sim642/adventofcode2024/Day14.scala
@@ -26,6 +26,13 @@ object Day14 {
     quadrants((1, 1)) * quadrants((-1, 1)) * quadrants((1, -1)) * quadrants((-1, -1))
   }
 
+  def findEasterEgg(robots: Seq[Robot], roomSize: Pos = Pos(101, 103)): Int = {
+    Iterator.from(0)
+      .map(t => robots.map(_.step(t, roomSize))) // TODO: optimize
+      .map(newRobots => newRobots.groupCount(_.pos))
+      .indexWhere(_.values.forall(_ <= 1)) // look for arrangement with unique positions
+  }
+
   def parseRobot(s: String): Robot = s match {
     case s"p=$pX,$pY v=$vX,$vY" =>
       Robot(Pos(pX.toInt, pY.toInt), Pos(vX.toInt, vY.toInt))
@@ -37,5 +44,6 @@ object Day14 {
 
   def main(args: Array[String]): Unit = {
     println(safetyFactor(parseRobots(input)))
+    println(findEasterEgg(parseRobots(input)))
   }
 }
diff --git a/src/test/scala/eu/sim642/adventofcode2024/Day14Test.scala b/src/test/scala/eu/sim642/adventofcode2024/Day14Test.scala
@@ -27,4 +27,8 @@ class Day14Test extends AnyFunSuite {
   test("Part 1 input answer") {
     assert(safetyFactor(parseRobots(input)) == 228690000)
   }
+
+  test("Part 2 input answer") {
+    assert(findEasterEgg(parseRobots(input)) == 7093)
+  }
 }