Shuffle some numbers using scala - possibly not the most efficient!

Shuffle in Scala

import scala.annotation.tailrec
import scala.util.Random

def shuffle (values: List[Int]): List[Int] = {
  val r = new Random()
  
  @tailrec
  def shuffle0 (values: List[Int], accum: List[Int] = List.empty): List[Int] = values match {
    case List(x) => x :: accum
    case h :: t =>
      val idx = r.nextInt(t.length)
      shuffle0 (t.updated(idx, h), t(idx) :: accum)
  }
  
  shuffle0 (values)
}

shuffle (List (1,2,3,4,5,6,7,8,9))