Question

Given a List such as

List(1, 2, 3, 4, 5, 6, 7)

what is the best way to split it into n sub-lists, putting items into each list in a round-robin fashion?

e.g. if n = 3, the result should be

List(List(1, 4, 7), List(2, 5), List(3, 6))

I thought there would be a method in the collections API to do this, but I can’t seem to find it.

Bonus points for classy one-liners 😉

Answer 1

scala> def round[T](l: List[T], n: Int) = (0 until n).map{ i => l.drop(i).sliding(1, n).flatten.toList }.toList
round: [T](l: List[T], n: Int)List[List[T]]

scala> round((1 to 7).toList, 3)
res4: List[List[Int]] = List(List(1, 4, 7), List(2, 5), List(3, 6))