不等長リストの入れ替え

/*
List(
    List(1,2,3,4),
    List(5,6,7,8),
    List(9,0)
)
↓
List(
    List(1,5,9),
    List(2,6,0),
    List(3,7),
    List(4,8)
)*/

case class Player(id: Int, name: String, score: Int)

val t: List[(Int, String, Int)] = 
    (1 to 17) zip ('a' to 'z') map (x => (x._1, x._2.toString, scala.util.Random.nextInt(100))) toList

val players = t.map(x => Player(x._1, x._2, x._3))

val sortedPlayers = players.sortBy(x => (- x.score, x.id))

def transpose[A](xs: List[List[A]]): List[List[A]] = xs.filter(_.nonEmpty) match {
    case Nil => Nil
    case ys: List[List[A]] => ys.map{ _.head }::transpose(ys.map{ _.tail })
}

transpose(sortedPlayers.grouped(4).toList)