Day 2 part 1

2/src/main/scala/is/kow/adventofcode/_2019/IntCode.scala

+package is.kow.adventofcode._2019
+
+import scala.annotation.tailrec
+
+class IntCode(ops: List[Int]) {
+  private final val ADD = 1
+  private final val MULT = 2
+  private final val END = 99
+
+  def execute(): List[Int] = {
+
+    @tailrec def process(acc: List[Int], opCount: Int): List[Int] = {
+      acc.drop(opCount * 4) match {
+        case ADD :: in1 :: in2 :: dest :: xs =>
+          println(s"add ${acc(in1)} to ${acc(in2)} and put at $dest -- $xs")
+          val result = acc(in1) + acc(in2)
+          process(acc.updated(dest, result), opCount + 1)
+        case MULT :: in1 :: in2 :: dest :: xs =>
+          println(s"mult ${acc(in1)} and ${acc(in2)} and put at $dest -- $xs")
+          val result = acc(in1) * acc(in2)
+          process(acc.updated(dest, result), opCount + 1)
+        case END :: xs =>
+          println("IT'S OVER")
+          acc
+        //return the new list?
+        case _ => throw new Exception("Unknown opcode")
+      }
+    }
+
+    process(ops, 0)
+  }
+
+
+}

2/src/main/scala/is/kow/adventofcode/_2019/Puzzle2.scala

+package is.kow.adventofcode._2019
+
+object Puzzle2 extends App {
+  val app = List(1, 0, 0, 3, 1, 1, 2, 3, 1, 3, 4, 3, 1, 5, 0, 3, 2, 10, 1, 19, 1, 19, 9, 23, 1, 23, 6, 27, 1, 9, 27, 31, 1, 31, 10, 35, 2, 13, 35, 39, 1, 39, 10, 43, 1, 43, 9, 47, 1, 47, 13, 51, 1, 51, 13, 55, 2, 55, 6, 59, 1, 59, 5, 63, 2, 10, 63, 67, 1, 67, 9, 71, 1, 71, 13, 75, 1, 6, 75, 79, 1, 10, 79, 83, 2, 9, 83, 87, 1, 87, 5, 91, 2, 91, 9, 95, 1, 6, 95, 99, 1, 99, 5, 103, 2, 103, 10, 107, 1, 107, 6, 111, 2, 9, 111, 115, 2, 9, 115, 119, 2, 13, 119, 123, 1, 123, 9, 127, 1, 5, 127, 131, 1, 131, 2, 135, 1, 135, 6, 0, 99, 2, 0, 14, 0)
+
+  val fixed = app.updated(1, 12).updated(2, 2)
+
+  val result = new IntCode(fixed).execute()
+
+  println("FINAL ANSWER: " + result.head)
+
+}

2/src/test/scala/_2019/Puzzle2Spec.scala

+package _2019
+
+import is.kow.adventofcode._2019.IntCode
+import org.junit.runner.RunWith
+import org.scalatest.funspec.AnyFunSpec
+import org.scalatestplus.junit.JUnitRunner
+
+@RunWith(classOf[JUnitRunner])
+class Puzzle2Spec extends AnyFunSpec {
+
+  describe("Day 2: part 1") {
+    Map(
+      List(1, 0, 0, 0, 99) -> List(2, 0, 0, 0, 99),
+      List(2, 3, 0, 3, 99) -> List(2, 3, 0, 6, 99),
+      List(2, 4, 4, 5, 99, 0) -> List(2, 4, 4, 5, 99, 9801),
+      List(1, 1, 1, 4, 99, 5, 6, 0, 99) -> List(30, 1, 1, 4, 2, 5, 6, 0, 99)
+    ).foreach(pair => {
+      it(s"given ${pair._1} produces ${pair._2}") {
+        assert(new IntCode(pair._1).execute() == pair._2)
+      }
+    })
+
+  }
+
+  describe("Puzzle 4: part 2") {
+  }
+}

settings.gradle.kts

-include("1")
-include("4")
+include("1", "2", "4")