sad cycle detector

sadCycle.scala

def sadCycle(n:Int, b:Int): List[Int] = {
    def transform(n:Int, b:Int): Int = 
        n.toString.toCharArray.map(x => (x.toInt-48, b)).map(x => scala.math.pow(x._1, x._2)).sum.toInt
        
    def loop(n:Int, b:Int, acc:List[Int]): List[Int] = {
        (acc.tail contains acc.head) match {
            case true  => acc
            case false => loop(transform(n, b), b, transform(n, b)::acc)
        }
    }
    loop(n, b, List(0))
}