added counting sort

[sgbasaraner]

hacktoberfest: I copied the comments from bubble_sort and left them as is (changed bubble_sort to counting_sort), and my counting sort implementation works with negative numbers too. if the comments will be a problem, notify me and I'd like to make the necessary changes.

[andrealmeid]

Hello @sgbasaraner,
I read your code and I found some issues that you might be interest to notice. Two main features of counting sort is linear time complexity and stability. But, when you do this loop in lines 32-33

for i in range(counting_arr_length):
    for j in range(length):

you are, in fact, running j * i times. This can easily achieve O(n²) time complexity, when i >= j.

When you create the array, you do

counting_arr_length = maximum + 1 + abs(minimum)

But we don't need all this positions, just maximum + 1 - minimum are enough to store all the values.

Finally, the stability. Stability in counting sort is an important feature because it makes counting sort useful to be used as a radix sort subroutine. The way you do it, you lose the previous information about the original order of the elements.

I suggest checking out some Wikipedia pages about sorting algorithms and Introduction to Algorithms by Cormen, Leiserson, Rivest and Stein to find more about stability and time complexity. I made my own version, check it out! (#165) Contact me if you have doubts or need more information :)