58 lines
1.3 KiB
Scala
58 lines
1.3 KiB
Scala
package aoc.day4
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import aoc._
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import scala.collection.mutable.Map
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case class Card(id: Int, winning: List[Int], got: List[Int]):
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lazy val won =
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val winSet = winning.toSet
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got.filter(winSet contains _)
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def pointValue =
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if won.isEmpty then 0 else 1L << (won.length - 1)
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object Parser extends CommonParser:
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val nums = rep1(num)
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val card = "Card " ~ num ~ ":" ~ nums ~ "|" ~ nums ^^ { case (_ ~ id ~ _ ~ winning ~ _ ~ got) =>
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Card(id, winning, got)
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}
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end Parser
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val cards = lines.map(l => Parser.parse(Parser.card, l).get).toSeq
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// Part 1
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def part1 =
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val res = cards.map(_.pointValue).sum
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println(res)
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// Part 2
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class Tails():
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private val map = Map[Int, Long]()
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var sum = 0L
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def add(tail: Int, copies: Long): Unit =
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sum += copies
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map.updateWith(tail)(v => Some(v.fold(copies)(_ + copies)))
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def filter(id: Int): Unit =
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map.remove(id).foreach { sum -= _ }
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end Tails
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@scala.annotation.tailrec
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def traverse(ids: Iterator[Card], tails: Tails, accum: Long = 0): Long =
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if !ids.hasNext then return accum
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val card = ids.next()
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val copies = 1 + tails.sum
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tails.add(card.id + card.won.length, copies)
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tails.filter(card.id)
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traverse(ids, tails, accum + copies)
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def part2 =
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val res = traverse(cards.toIterator, new Tails())
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println(res)
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@main def Day4(part: Int) = part match
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case 1 => part1
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case 2 => part2
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