Fix issue trekhleb#105.

Author: trekhleb

README.md

@@ -272,7 +272,7 @@ Below is the list of some of the most used Big O notations and their performance
 | **Selection sort**    | n<sup>2</sup>   | n<sup>2</sup>       | n<sup>2</sup>       | 1         | No        |           |
 | **Heap sort**         | n&nbsp;log(n)   | n&nbsp;log(n)       | n&nbsp;log(n)       | 1         | No        |           |
 | **Merge sort**        | n&nbsp;log(n)   | n&nbsp;log(n)       | n&nbsp;log(n)       | n         | Yes       |           |
-| **Quick sort**        | n&nbsp;log(n)   | n&nbsp;log(n)       | n<sup>2</sup>       | log(n)    | No        |           |
+| **Quick sort**        | n&nbsp;log(n)   | n&nbsp;log(n)       | n<sup>2</sup>       | log(n)    | No        | Quicksort is usually done in-place with O(log(n)) stack space |
 | **Shell sort**        | n&nbsp;log(n)   | depends on gap sequence   | n&nbsp;(log(n))<sup>2</sup>  | 1         | No         |           |
 | **Counting sort**     | n + r           | n + r               | n + r               | n + r     | Yes       | r - biggest number in array |
 | **Radix sort**        | n * k           | n * k               | n * k               | n + k     | Yes       | k - length of longest key |

src/algorithms/sorting/quick-sort/README.md

@@ -27,7 +27,7 @@ The horizontal lines are pivot values.
 
 | Name                  | Best            | Average             | Worst               | Memory    | Stable    | Comments  |
 | --------------------- | :-------------: | :-----------------: | :-----------------: | :-------: | :-------: | :-------- |
-| **Quick sort**        | n&nbsp;log(n)   | n&nbsp;log(n)       | n<sup>2</sup>       | log(n)    | No        |           |
+| **Quick sort**        | n&nbsp;log(n)   | n&nbsp;log(n)       | n<sup>2</sup>       | log(n)    | No        |  Quicksort is usually done in-place with O(log(n)) stack space |
 
 ## References