97 lines
2.6 KiB
Scala
97 lines
2.6 KiB
Scala
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package aoc
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package day12
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import scala.annotation.tailrec
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import scala.collection.mutable
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import util.chaining.*
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val dayNumber = "12"
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@main def part1: Unit =
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println(part1(loadInput(dayNumber)))
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@main def part2: Unit =
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println(part2(loadInput(dayNumber)))
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def part1(input: String): String =
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def generateArrangements(cond: String): List[String] =
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@tailrec def aux(acc: List[String], remaining: String): List[String] =
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remaining.headOption match
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case None => acc
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case Some('?') =>
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aux(
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(acc.map(_ + '#') ++ acc.map(_ + '.')),
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remaining.tail
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)
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case Some('#') =>
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aux(acc.map(_ + '#'), remaining.tail)
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case Some('.') =>
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aux(acc.map(_ + '.'), remaining.tail)
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case _ => ??? // Can't happen
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aux(List(""), cond)
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def isValid(arr: String, groups: Array[Int]): Boolean =
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arr
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.split('.')
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.filter(_.nonEmpty)
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.map(_.length)
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.corresponds(groups)(_ == _)
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input
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.split('\n')
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.map { case s"$cond $groups" =>
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generateArrangements(cond) -> groups.split(',').map(_.toInt)
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}
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.map((arrs, groups) => arrs.count(isValid(_, groups)))
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.sum
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.toString
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def part2(input: String): String =
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def countArrangements(
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cond: String,
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groups: List[Int]
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): Long =
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val cache = mutable.Map.empty[(List[Char], List[Int], Int), Long]
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def countCached(cond: List[Char], groups: List[Int], curGroup: Int): Long =
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cache.getOrElseUpdate(
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(cond, groups, curGroup),
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count(cond, groups, curGroup)
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)
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def count(cond: List[Char], groups: List[Int], curGroup: Int): Long =
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if cond.isEmpty then
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if curGroup == 0 && groups.isEmpty || groups == List(curGroup) then 1
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else 0
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else
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cond.head match
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case '?' =>
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countCached('#' +: cond.tail, groups, curGroup) +
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countCached('.' +: cond.tail, groups, curGroup)
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case '#' =>
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if groups.headOption.contains(curGroup) then 0
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else countCached(cond.tail, groups, curGroup + 1)
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case '.' =>
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if groups.headOption.contains(curGroup) then
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countCached(cond.tail, groups.tail, 0)
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else if curGroup == 0 then countCached(cond.tail, groups, 0)
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else 0
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case _ => ??? // Can't happen
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countCached(cond.toList, groups, 0)
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input
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.split('\n')
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.map { case s"$cond $groups" =>
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cond -> groups.split(',').map(_.toInt).toList
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}
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.map((cond, groups) =>
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countArrangements(
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List.fill(5)(cond).mkString("?"),
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List.fill(5)(groups).flatten
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)
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)
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.sum
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.toString
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