Using a Recursion Tree to solve the recurrence $T(n) = \sqrt n T(\frac{n}{2}) + 10n$?

491 Views Asked by At

I am attempting to solve the above recurence by giving tight $\Theta$ bounds.

Assume that the logs here are all base 2!

To solve a recursion tree as far as I understand, I need two things.

  1. The height of the tree
  2. Work or Computation per level of the tree

The product of these 1. and 2. will tell me how the recurrence scales.

As for part 1.)

I was able to gauge that $n^\frac{1}{2h} = 2$ where an input with size 2 is my base case, and $h$ is the height of the tree.

Then, $h \approx \frac{log_2(n)}{2}$

I have issues with finding the work per level of the tree however, since this value changes depending which level of the tree you are on. I come to find that it is $n^\frac{1}{2i}10n^\frac{1}{2i}$

Where $i$ is the level of the tree you are looking at.

However, how do I use this information to solve the recurrence?