merge sort without extra memory

Question

is there any condition in which merge sort can be done without extra memory my prof said it has and he will give bonus point on that.

Answer 1

Given that this is a homework question, I can only point you to The Art of Computer Programming. A good programmer should be able to use the standard references in our field to research a question such as this.

Answer 2

You want to google in place merge sort.

Here is one of the result : http://thomas.baudel.name/Visualisation/VisuTri/inplacestablesort.html

Answer 3

Yes, the answer to this is to use in-place merge sort