Refactor article about `asymptotic notation`

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3.6. $O(2^n)$ - Exponential Time

Example:

Tower of Hanoi

3.7. $O(n!)$ - Factorial Time

Example:

Determinant Expansion by Minors, Brute force Search algorithm for Traveling Salesman Problem.

3.8. $O(n^m)$ - Polynomial Time

Example:

Strassen’s Matrix Multiplication, Bubble Sort, Selection Sort, Insertion Sort, Bucket Sort.

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Closed by #168