Day3

README.md

@@ -13,7 +13,7 @@ Advent of Code 2024 in Scala 3 (first time using Scala). Completion is not guara
 |-----|--------------|
 | 1   | ⭐️⭐️         |
 | 2   | ⭐️⭐️         |
-| 3   | ❌            |
+| 3   | ⭐️⭐️         |
 | 4   | ❌            |
 | 5   | ❌            |
 | 6   | ❌            |

src/main/scala/net/rohlandm/aoc24/application/Day3Solver.scala

@@ -1,5 +1,41 @@
 package net.rohlandm.aoc24.application
 
+import net.rohlandm.aoc24.application.Execution.ENABLED
 import net.rohlandm.aoc24.domain.DaySolver
 
-class Day3Solver extends DaySolver(3)
+class Day3Solver extends DaySolver(3):
+
+  private val mulPattern = """mul\((\d+),(\d+)\)""".r
+  private val conditionalMulPattern = """mul\((\d+),(\d+)\)|do\(\)|don't\(\)""".r
+
+  override def solvePart1(input: List[String]): Option[Long] =
+    val instructions = input.flatMap(mulPattern.findAllIn(_))
+    Some(instructions.map(executeInstruction).sum)
+
+  override def solvePart2(input: List[String]): Option[Long] =
+    val instructions = input.flatMap(conditionalMulPattern.findAllIn(_))
+    var execution = ENABLED
+    var acc: Long = 0
+
+    instructions.foreach(instruction => {
+      val result = executeConditionally.apply(instruction, execution, acc)
+      acc = result._1
+      execution = result._2
+    })
+
+    Some(acc)
+
+  private val executeInstruction = (instruction: String) =>
+    val split = instruction.split("[(),]").toList
+    var execution = Execution.ENABLED
+    split.apply(1).toInt * split.apply(2).toInt
+
+  private val executeConditionally = (instruction: String, execution: Execution, acc: Long) =>
+    instruction match
+      case "do()" => (acc, Execution.ENABLED)
+      case "don't()" => (acc, Execution.DISABLED)
+      case mul if execution == ENABLED => (acc + executeInstruction.apply(mul), execution)
+      case _ => (acc, execution)
+
+enum Execution:
+  case ENABLED, DISABLED

src/test/scala/net/rohlandm/aoc24/application/Day3SolverTest.scala

@@ -7,11 +7,14 @@ import org.scalatest.funsuite.AnyFunSuiteLike
  */
 class Day3SolverTest extends AnyFunSuiteLike:
 
-  private val testInput =
-    """""".stripMargin.split("\n").toList
+  private val testInput1 =
+    """xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))""".stripMargin.split("\n").toList
+
+  private val testInput2 =
+    """xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))""".stripMargin.split("\n").toList
 
   test("solvePart1 returns result"):
-    assert(Day3Solver().solvePart1(testInput) === None)
+    assert(Day3Solver().solvePart1(testInput1) === Some(161))
 
   test("solvePart2 returns result"):
-    assert(Day3Solver().solvePart2(testInput) === None)
+    assert(Day3Solver().solvePart2(testInput2) === Some(48))