[erlang-questions] concentate solution well ??

[Roelof Wobben]

Hello,

I have this exercise of the Erlang programming book.

Write a function that, given a list of lists, will concatenate them.
Example:
concatenate([[1,2,3], [], [4, five]]) ⇒ [1,2,3,4,five].
Hint: you will have to use a helpfunction and concatenate the lists in 
several steps.

But I do not need to use a helper function because it can be solved like 
this :

concatenate( [List1 , List2 , List3] ) ->
     List1 ++ List2 ++ List3.

Or is this not the solution that is meant on this exercise ?
Do I need to solve it by using pattern matching ?

Roelof