Solve 2023 day 6 part 2

src/main/scala/eu/sim642/adventofcode2023/Day6.scala

@@ -2,25 +2,33 @@ package eu.sim642.adventofcode2023
 
 object Day6 {
 
-  case class Race(time: Int, recordDistance: Int) {
-    def wins: Int = {
-      (0 to time).count(t => t * (time - t) > recordDistance)
-    }
+  case class Race(time: Long, recordDistance: Long) {
+    def wins: Long = // TODO: optimize with math
+      (0L to time).count(t => t * (time - t) > recordDistance)
+
+    def ++(that: Race): Race =
+      Race(
+        (time.toString + that.time.toString).toLong,
+        (recordDistance.toString + that.recordDistance.toString).toLong
+      )
   }
 
-  def multiplyRaceWins(races: Seq[Race]): Int = races.map(_.wins).product
+  def multiplyRaceWins(races: Seq[Race]): Long = races.map(_.wins).product
+
+  def concatenatedRaceWin(races: Seq[Race]): Long = races.reduce(_ ++ _).wins
 
 
   def parseRaces(input: String): Seq[Race] = input.linesIterator.toSeq match {
     case Seq(s"Time:$timesStr", s"Distance:$distancesStr") =>
-      val times = timesStr.trim.split(" +").map(_.toInt).toSeq
-      val distances = distancesStr.trim.split(" +").map(_.toInt).toSeq
+      val times = timesStr.trim.split(" +").map(_.toLong).toSeq
+      val distances = distancesStr.trim.split(" +").map(_.toLong).toSeq
       (times lazyZip distances).map(Race.apply)
   }
 
   lazy val input: String = io.Source.fromInputStream(getClass.getResourceAsStream("day6.txt")).mkString.trim
 
   def main(args: Array[String]): Unit = {
     println(multiplyRaceWins(parseRaces(input)))
+    println(concatenatedRaceWin(parseRaces(input)))
   }
 }

src/test/scala/eu/sim642/adventofcode2023/Day6Test.scala

@@ -16,4 +16,12 @@ class Day6Test extends AnyFunSuite {
   test("Part 1 input answer") {
     assert(multiplyRaceWins(parseRaces(input)) == 2756160)
   }
+
+  test("Part 2 examples") {
+    assert(concatenatedRaceWin(parseRaces(exampleInput)) == 71503)
+  }
+
+  test("Part 2 input answer") {
+    assert(concatenatedRaceWin(parseRaces(input)) == 34788142)
+  }
 }