Solve 2024 day 13 part 2

sim642 · Dec 13, 2024 · 0df8f3c · 0df8f3c
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diff --git a/src/main/scala/eu/sim642/adventofcode2024/Day13.scala b/src/main/scala/eu/sim642/adventofcode2024/Day13.scala
@@ -2,51 +2,73 @@ package eu.sim642.adventofcode2024
 
 import eu.sim642.adventofcodelib.graph.{Dijkstra, GraphSearch, TargetNode}
 import eu.sim642.adventofcodelib.pos.Pos
-import eu.sim642.adventofcodelib.IntegralImplicits._
+import eu.sim642.adventofcodelib.IntegralImplicits.*
+import eu.sim642.adventofcodelib.NumberTheory
 
 object Day13 {
 
-  case class ClawMachine(buttonA: Pos, buttonB: Pos, prize: Pos)
+  case class LongPos(x: Long, y: Long)
 
-  def minWinTokens(clawMachine: ClawMachine): Int = {
-    val ClawMachine(buttonA, buttonB, prize) = clawMachine
+  case class ClawMachine(buttonA: Pos, buttonB: Pos, prize: LongPos)
 
-    /*val graphSearch = new GraphSearch[Pos] with TargetNode[Pos] {
-      override val startNode: Pos = Pos.zero
+  trait Part {
+    def minWinTokens(clawMachine: ClawMachine): Long
 
-      override def neighbors(pos: Pos): IterableOnce[(Pos, Int)] = {
-        for {
-          (button, tokens) <- Seq(clawMachine.buttonA -> 3, clawMachine.buttonB -> 1)
-          newPos = pos + button
-          if newPos <= targetNode
-        } yield newPos -> tokens
+    def sumMinWinTokens(clawMachines: Seq[ClawMachine]): Long = clawMachines.map(minWinTokens).sum
+  }
+
+  object Part1 extends Part {
+    override def minWinTokens(clawMachine: ClawMachine): Long = {
+      val ClawMachine(buttonA, buttonB, prize) = clawMachine
+
+      /*val graphSearch = new GraphSearch[Pos] with TargetNode[Pos] {
+        override val startNode: Pos = Pos.zero
+
+        override def neighbors(pos: Pos): IterableOnce[(Pos, Int)] = {
+          for {
+            (button, tokens) <- Seq(clawMachine.buttonA -> 3, clawMachine.buttonB -> 1)
+            newPos = pos + button
+            if newPos <= targetNode
+          } yield newPos -> tokens
+        }
+
+        override val targetNode: Pos = clawMachine.prize
       }
 
-      override val targetNode: Pos = clawMachine.prize
-    }
+      Dijkstra.search(graphSearch).target.map(_._2).getOrElse(0)*/
 
-    Dijkstra.search(graphSearch).target.map(_._2).getOrElse(0)*/
+      /*(for {
+        timesA <- 0 to 100
+        prizeB = prize - timesA *: buttonA
+        timesB <- prizeB.x /! buttonB.x
+        if timesB * buttonB.y == prizeB.y
+      } yield 3 * timesA + timesB).minOption.getOrElse(0)*/
 
-    (for {
-      timesA <- 0 to 100
-      prizeB = prize - timesA *: buttonA
-      timesB <- prizeB.x /! buttonB.x
-      if timesB * buttonB.y == prizeB.y
-    } yield 3 * timesA + timesB).minOption.getOrElse(0)
+      (for {
+        timesB <- (prize.x * buttonA.y - prize.y * buttonA.x) /! (buttonB.x * buttonA.y - buttonB.y * buttonA.x)
+        timesA <- (prize.x - timesB * buttonB.x) /! buttonA.x
+      } yield 3 * timesA + timesB).getOrElse(0)
+    }
   }
 
-  def sumMinWinTokens(clawMachines: Seq[ClawMachine]): Int = clawMachines.map(minWinTokens).sum
+  object Part2 extends Part {
+    override def minWinTokens(clawMachine: ClawMachine): Long = {
+      val newClawMachine = clawMachine.copy(prize = LongPos(clawMachine.prize.x + 10000000000000L, clawMachine.prize.y + 10000000000000L))
+      Part1.minWinTokens(newClawMachine)
+    }
+  }
 
   def parseClawMachine(s: String): ClawMachine = s match {
     case s"Button A: X+$aX, Y+$aY\nButton B: X+$bX, Y+$bY\nPrize: X=$pX, Y=$pY" =>
-      ClawMachine(Pos(aX.toInt, aY.toInt), Pos(bX.toInt, bY.toInt), Pos(pX.toInt, pY.toInt))
+      ClawMachine(Pos(aX.toInt, aY.toInt), Pos(bX.toInt, bY.toInt), LongPos(pX.toLong, pY.toLong))
   }
 
   def parseClawMachines(input: String): Seq[ClawMachine] = input.split("\n\n").map(parseClawMachine).toSeq
 
   lazy val input: String = scala.io.Source.fromInputStream(getClass.getResourceAsStream("day13.txt")).mkString.trim
 
   def main(args: Array[String]): Unit = {
-    println(sumMinWinTokens(parseClawMachines(input)))
+    println(Part1.sumMinWinTokens(parseClawMachines(input)))
+    println(Part2.sumMinWinTokens(parseClawMachines(input)))
   }
 }
diff --git a/src/test/scala/eu/sim642/adventofcode2024/Day13Test.scala b/src/test/scala/eu/sim642/adventofcode2024/Day13Test.scala
@@ -23,10 +23,18 @@ class Day13Test extends AnyFunSuite {
       |Prize: X=18641, Y=10279""".stripMargin
 
   test("Part 1 examples") {
-    assert(sumMinWinTokens(parseClawMachines(exampleInput)) == 480)
+    assert(Part1.sumMinWinTokens(parseClawMachines(exampleInput)) == 480)
   }
 
   test("Part 1 input answer") {
-    assert(sumMinWinTokens(parseClawMachines(input)) == 31623)
+    assert(Part1.sumMinWinTokens(parseClawMachines(input)) == 31623)
+  }
+
+  test("Part 2 examples") {
+    assert(Part2.sumMinWinTokens(parseClawMachines(exampleInput)) == 875318608908L) // from IRC
+  }
+
+  test("Part 2 input answer") {
+    assert(Part2.sumMinWinTokens(parseClawMachines(input)) == 93209116744825L)
   }
 }