Otra forma de implementar validar

validar.scala

def validar(tam:Int, accion:String) : Option[Array[Int]] = 
  if (accion.exists(c => !c.isDigit) None
  else {
    val num = accion.map(c => c.toInt - '0'.toInt).distinct
    if (num.length == tam && num.length == accion.length)
      Some(num.toArray)
    else
      None
  }