Thanks for submitting this!
I think what I meant here by “extra” space is the additional space taken up in addition to the space needed to solve the actual problem. That is, the goal of these functions is to produce an array containing data. So, we have to use up a certain amount of space in order to solve a problem - there’s no way to get around that. However, the text is focusing on the “extra” space - that is additional space consumed that isn’t part of the actual output of the function.
Perhaps I can help clarify the wording here in a future version.
Thanks again,
Jay