Day 2

aoc/src/Day2.scala

@@ -0,0 +1,91 @@
+import scala.io.Source
+
+object Day2 extends App:
+
+  val input = Source
+    .fromURL(getClass.getResource("day2Input.txt"))
+    .mkString
+    .split('\n')
+    .toList
+
+  enum Move:
+    case Rock, Paper, Scissors
+
+  object Move:
+    val parse: Char => Move =
+      case 'A' => Rock
+      case 'X' => Rock
+      case 'B' => Paper
+      case 'Y' => Paper
+      case 'C' => Scissors
+      case 'Z' => Scissors
+
+    val loosingCounterpart: Move => Move =
+      case Rock     => Scissors
+      case Paper    => Rock
+      case Scissors => Paper
+
+    val winningCounterpart: Move => Move =
+      case Rock     => Paper
+      case Paper    => Scissors
+      case Scissors => Rock
+
+    val points: Move => Int =
+      case Rock     => 1
+      case Paper    => 2
+      case Scissors => 3
+
+  enum MatchResult:
+    case Win, Loss, Draw
+
+  object MatchResult:
+    val parse: Char => MatchResult =
+      case 'X' => Loss
+      case 'Y' => Draw
+      case 'Z' => Win
+
+  object Part1:
+    val guide = input
+      .map(game => Game(Move.parse(game.head), Move.parse(game.last)))
+
+    import Move.*
+    import MatchResult.*
+
+    final case class Game(opponent: Move, self: Move):
+      val result =
+        if self == opponent then Draw
+        else if Move.loosingCounterpart(self) == opponent then Win
+        else Loss
+
+      val points = result match
+        case Win  => 6 + Move.points(self)
+        case Loss => Move.points(self)
+        case Draw => 3 + Move.points(self)
+
+    val totalScore = guide.map(_.points).sum
+
+  println(s"Part 1: ${Part1.totalScore}")
+
+  object Part2:
+    val guide = input
+      .map(game => Game(Move.parse(game.head), MatchResult.parse(game.last)))
+
+    import Move.*
+    import MatchResult.*
+
+    final case class Game(opponent: Move, targetResult: MatchResult):
+
+      val self =
+        if targetResult == Draw then opponent
+        else if targetResult == Win then Move.winningCounterpart(opponent)
+        else Move.loosingCounterpart(opponent)
+
+      val points = targetResult match
+        case Win  => 6 + Move.points(self)
+        case Loss => Move.points(self)
+        case Draw => 3 + Move.points(self)
+
+    val totalScore = guide.map(_.points).sum
+
+  println(s"Part 2: ${Part2.totalScore}")
+end Day2