quicksort

Quicksort Algorithm Implementation with Python

QuickSort is an O(nlogn) efficient sorting algorithm, serving as systematic method for placing elements of an array in order. Quicksort is a comparison sort, meaning that it can sort items of any type for which a “less-than” relation (formally, a total order) is defined. In efficient implementations it is not a stable sort, meaning that the relative order of equal sort items is not preserved. Quicksort can operate in-place on an array, requiring small additional amounts of memory to perform the sorting. It is very similar to selection sort, except that it does not always choose worst-case partition.

Source: https://en.wikipedia.org/wiki/Quicksort
Below are 2 versions of the Quicksort Algorithm Implementation with Python. The first version is easy, but use more memory. The second version use the memory very efficiently.

I- QuickSort Algorithm Implementation with Python (Memory intensive version)

QuickSort Algorithm Implementation with Python method1

Output:

II- Quicksort Algorithm Implementation with Python (with Memory Optimisation)

III- QuickSort Algorithm Implementation with Python for Both Methods with duration captured

Output

III- Most Efficient Quicksort implementation in Python on array of integer represented as string. Example: array=[“1″,”237373737″,”3″,”1971771717171717″,”0”]

def QuickSort(array):

return array.sort(key=lambda x: (len(x),x))

input:

6
31415926535897932384626433832795
1
3
10
3
5

Output:

1
3
3
5
10
31415926535897932384626433832795

Just to clarify that lambda part, in case someone else doesn't understand how exactly string comparison works: '2' > '1' is True, but '2' > '10' is also True, as well as '2' > '1000'. That's why the strings are sorted by length first, because len('2') < len('10'). IV- Build up a sorted array, one element at a time. Print the array after each iteration of the insertion sort, i.e., whenever the next element has been inserted at its correct position

Python build up sorted array

python build up sorted array input output

Etienne Noumen

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