AoC day 20

import io.Source

object day20 extends App {

  case class Range(val from: Long, val to: Long)

  def merge(rs: List[Range], sep: List[Range] = Nil): List[Range] = rs match {
    case x :: y :: t =>
      if (y.from > x.to + 1) merge(y :: t, x :: sep)
      else merge(Range(x.from, x.to max y.to) :: t, sep)
    case _ => (rs ::: sep).reverse
  }

  def whitelisted(rs: List[Range], acc: Long = 0): Long = rs match {
    case _ :: Nil => acc
    case h :: x :: t => whitelisted(x :: t, acc + x.from - h.to - 1)
  }

  val input = Source.fromFile("day20.txt").getLines.toList
  val ranges = input.map(i => i.split('-')).map(i => Range(i.head.toLong, i.last.toLong))

  val merged = merge(ranges.sortBy(_.from))
  println(merged.head.to + 1)
  println(whitelisted(merged))

}