如何在Scala中展平List [Any，List []]

Question

val xs = List(List(4, List(4, 7)), List(3, List(3, 5)), List(4, List(5, 9))

如何将其转换为：

List(List(4, 4, 7), List(3, 3, 5), List(4, 5, 9))

Answer 1

这样的东西？

xs.map(arr => arr.foldLeft(List[Any]())((acc, value) => value match {
    case xs:List[Any] => acc ++ xs
    case x:Any => acc :+ x
}))