PlusMinusDouble.scala

// http://nabetani.sakura.ne.jp/hena/ord13updowndouble/

object PlusMinusDouble extends App {

  def solve(list: List[(Int, Int)]): Int = list match {
    case (n, 0) :: _ => n
    case (n, x) :: xs if x % 2 != 0 =>
      solve(xs :+ (n+1, x+1) :+ (n+1, x-1))
    case (n, x) :: xs =>
      solve(xs :+ (n+1, x/2))
  }

  val problem = args(0).toInt

  println(solve(List((0, problem))))
}