Aoc2021-day6.scala

package lascala.aoc2021.day1_10.day6

opaque type School = Map[Int, BigInt]

extension (s: School)
  def next: School =
    val current: School = for (remainingDates, count) <- s if remainingDates > 0
    yield (remainingDates - 1, count)

    s.get(0).fold(current) { zeroesCount =>
      current +
        (6 -> (zeroesCount + current.getOrElse(6, 0))) +
        (8 -> zeroesCount)
    }
  end next

  def total: BigInt = s.values.sum

  def day(n: Int): School =
    (0 until n).foldLeft(s)((school, _) => school.next)
end extension

object School:
  def parse(s: String): School =
    s.split(",").groupBy(_.toInt).mapValues(x => BigInt(x.size)).toMap

def solve1(s: String): BigInt =
  School.parse(s).day(80).total
end solve1

def solve2(s: String): BigInt =
  School.parse(s).day(256).total
end solve2

@main def part1: Unit =
  val ans = solve1(input)
  println(ans)

@main def part2: Unit =
  val ans = solve2(input)
  println(ans)

// val input =
 

Aoc2021-day6Test.scala

package lascala.aoc2021.day1_10.day6

import minitest.SimpleTestSuite
import hedgehog.minitest.HedgehogSupport
import hedgehog.*

object Day6Test extends SimpleTestSuite with HedgehogSupport:

  val testInput = """3,4,3,1,2"""

  example("day6 - solve1") {
    solve1(testInput) ==== 5934
  }

  example("day6 - solve2") {
    solve2(testInput) ==== BigInt("26984457539")
  }
end Day6Test