# Am I drawing the recursion trees correctly?

I guess I've already figured out what is a recursion tree and how to construct one. Inspired by Figure 2.5 of "Introduction to Algorithms, 3rd Edition by CLRS", I drew some recursion trees for the recurrence $$T(n) = 2T(n/2) + cn$$.

the recursion tree for the recurrence when n=16

the recursion tree for the recurrence when n=13

the recursion tree for the recurrence when n=7

Could someone help double-check my understanding?

$$T(n/2)$$ is not well-defined if $$n$$ is odd. The merge sort recurrence - if you want to take floors and ceilings into account - is actually $$T(n) = T(\lceil n/2 \rceil) + T(\lfloor n/2 \rfloor) + cn$$. So, if $$n=13$$, the subproblems would have sizes $$7$$ and $$6$$, respectively (not $$8$$ and $$5$$, respectively).
It’s ok to be sloppy and assume $$n$$ is a power of $$2$$ because that doesn’t affect the final conclusions. Recursion trees are usually drawn with this simplifying assumption, and the intuition carries over to the general case.