Year 2015 Day 22

Author: maneatingape

README.md

@@ -231,3 +231,4 @@ The minimal SBT project provides:
 | 19 | [Medicine for Rudolph](https://adventofcode.com/2015/day/19) | [Source](src/main/scala/AdventOfCode2015/Day19.scala) |
 | 20 | [Infinite Elves and Infinite Houses](https://adventofcode.com/2015/day/20) | [Source](src/main/scala/AdventOfCode2015/Day20.scala) |
 | 21 | [RPG Simulator 20XX](https://adventofcode.com/2015/day/21) | [Source](src/main/scala/AdventOfCode2015/Day21.scala) |
+| 22 | [Wizard Simulator 20XX](https://adventofcode.com/2015/day/22) | [Source](src/main/scala/AdventOfCode2015/Day22.scala) |

src/main/resources/AdventOfCode2015/Day22.txt

@@ -0,0 +1,2 @@
+Hit Points: 55
+Damage: 8

src/main/scala/AdventOfCode2015/Day22.scala

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+package AdventOfCode2015
+
+object Day22:
+  val MagicMissile = Spell(53, 1)
+  val Drain = Spell(73, 1)
+  val Shield = Spell(113, 6)
+  val Poison = Spell(173, 6)
+  val Recharge = Spell(229, 5)
+  val spells = Set(MagicMissile, Drain, Shield, Poison, Recharge)
+
+  case class Spell(cost: Int, duration: Int)
+
+  case class State(hero: Int, mana: Int, spent: Int, armor: Int, boss: Int, damage: Int, active: Map[Spell, Int]):
+    def applyEffects: State = active.foldLeft(copy(armor = 0)) { case (state, (spell, duration)) =>
+      val next = state.effect(spell)
+      if duration == 1 then next.copy(active = state.active.removed(spell))
+      else next.copy(active = state.active.updated(spell, duration - 1))
+    }
+    def effect(spell: Spell): State = spell match
+      case MagicMissile => copy(boss = boss - 4)
+      case Drain => copy(hero = hero + 2, boss = boss - 2)
+      case Shield => copy(armor = 7)
+      case Poison => copy(boss = boss - 3)
+      case Recharge => copy(mana = mana + 101)
+    def heroTurn(spell: Spell): State = copy(mana = mana - spell.cost, spent = spent + spell.cost, active = active + (spell -> spell.duration))
+    def bossTurn: State = copy(hero = hero - (damage - armor).max(1))
+    def hardMode: State = copy(hero = hero - 1)
+
+  def parse(input: Seq[String]): State =
+    val Seq(health, damage) = input.map(_.filter(_.isDigit).toInt)
+    State(50, 500, 0, 0, health, damage, Map())
+
+  def fight(start: State, hard: Boolean): Int =
+    var result = Int.MaxValue
+
+    def helper(state: State, playerTurn: Boolean): Unit =
+      val first = if hard && playerTurn then state.hardMode else state
+      val second = first.applyEffects
+
+      if first.spent >= result || first.hero <= 0 then ()
+      else if second.boss <= 0 then result = result.min(second.spent)
+      else if !playerTurn then helper(second.bossTurn, !playerTurn)
+      else spells
+        .diff(second.active.keySet)
+        .filter(_.cost <= second.mana)
+        .foreach(spell => helper(second.heroTurn(spell), !playerTurn))
+    end helper
+
+    helper(start, true)
+    result
+  end fight
+
+  def part1(input: Seq[String]): Int = fight(parse(input), false)
+
+  def part2(input: Seq[String]): Int = fight(parse(input), true)
+
+  def main(args: Array[String]): Unit =
+    val data = io.Source.fromResource("AdventOfCode2015/Day22.txt").getLines().toSeq
+    println(part1(data))
+    println(part2(data))

src/test/scala/AdventOfCode2015/Day22Suite.scala

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+package AdventOfCode2015
+
+import org.scalatest.funsuite.AnyFunSuite
+
+class Day22Suite extends AnyFunSuite
+// No unit tests possible