Update READMEs.

Author: trekhleb

README.md

@@ -234,9 +234,9 @@ Below is the list of some of the most used Big O notations and their performance
 | **Bubble sort**       | n               | n<sup>2</sup>       | n<sup>2</sup>       | 1         | Yes       |           |
 | **Insertion sort**    | n               | n<sup>2</sup>       | n<sup>2</sup>       | 1         | Yes       |           |
 | **Selection sort**    | n<sup>2</sup>   | n<sup>2</sup>       | n<sup>2</sup>       | 1         | No        |           |
-| **Heap sort**         | n log(n)        | n log(n)            | n log(n)            | 1         | No        |           |
-| **Merge sort**        | n log(n)        | n log(n)            | n log(n)            | n         | Yes       |           |
-| **Quick sort**        | n log(n)        | n log(n)            | n<sup>2</sup>       | log(n)    | No        |           |
-| **Shell sort**        | n log(n)        | depends on gap sequence   | n (log(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        |           |
+| **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 |