Is there a safe way in Scala to transpose a List of unequal-length Lists?

Question

Given the following List:

val l = List(List(1, 2, 3), List(4, 5), List(6, 7, 8))

If I try to transpose it, Scala will throw the following e

Answer 1

How about this one-liner using the Scala's standard Api:

((l map (_.toArray)) toArray).transpose map (_.toList) toList

This gets the job done and is O(N*M), where N is the length of the wrapper list and M is the length of the longest list inside the wrapper list.