2022 Day 2 Scala

2022/day2.scala

@@ -0,0 +1,50 @@
+import scala.io.Source
+import scala.math.floorMod
+
+enum RPS(val score: Int):
+	case Rock     extends RPS(1)
+	case Paper    extends RPS(2)
+	case Scissors extends RPS(3)
+
+	def <=>(other: RPS) =
+		(other.score - score) match
+			case -2 | 1 => -1
+			case -1 | 2 =>  1
+			case _      =>  0
+
+	def >(other: RPS) = <=>(other) > 0
+	def <(other: RPS) = <=>(other) < 0
+	def ==(other: RPS) = <=>(other) == 0
+
+	def +(amount: Int) = RPS.fromOrdinal(floorMod(this.ordinal + amount, 3))
+	def -(amount: Int) = RPS.fromOrdinal(floorMod(this.ordinal - amount, 3))
+
+def resultScore(a: RPS, b: RPS) = a <=> b match
+	case -1 => 0
+	case 1 => 6
+	case _ => 3
+
+val moveMap = Map("A"->RPS.Rock, "B"->RPS.Paper, "C"->RPS.Scissors, "X"->RPS.Rock, "Y"->RPS.Paper, "Z"->RPS.Scissors)
+
+@main def main() =
+	val strategyGuide = Source.fromFile("day2-input").getLines.map(_.split(" ")).toArray  // Can't leave it lazy as Part 1 will consume it
+	// val strategyGuide = Source.fromString("A Y\nB X\nC Z\n").getLines.map(_.split(" ")).toArray
+
+	// Part 1 - evaluate all moves in the guide using moveMap and tally score
+	var score = 0
+	for movePair <- strategyGuide do
+		val opponentMove = moveMap(movePair(0))
+		val ourMove = moveMap(movePair(1))
+		score += resultScore(ourMove, opponentMove) + ourMove.score
+	println(score)
+
+	// Part 2 - X->lose, Y->draw, Z->win
+	score = 0
+	for movePair <- strategyGuide do
+		val opponentMove = moveMap(movePair(0))
+		val ourMove = movePair(1) match
+			case "X" => opponentMove - 1
+			case "Y" => opponentMove
+			case "Z" => opponentMove + 1
+		score += resultScore(ourMove, opponentMove) + ourMove.score
+	println(score)