Space requirements of a merge-sort

Question

I\'m trying to understand the space requirements for a Mergesort, O(n).
I see that time requirements are basically, amount of levels(logn) * merge(n) so that makes (n lo

Answer 1

There are versions of merge-sort that can work in place.

However, in most implementations the space is linear in the size of the array. That means n for the first level, n/2 for the second, n/4 for the third, etc. By the time you are at the bottom of your recursion, this series adds up to about 2n, which is linear.