gnome_sort.py

"""
Gnome Sort Algorithm (A.K.A. Stupid Sort)

This algorithm iterates over a list comparing an element with the previous one.
If order is not respected, it swaps element backward until order is respected with
previous element.  It resumes the initial iteration from element new position.

For doctests run following command:
python3 -m doctest -v gnome_sort.py

For manual testing run:
python3 gnome_sort.py
Gnome Sort Algorithm implementation in Python.

Gnome sort (also called Stupid Sort) works by comparing the current element
with the previous one. If they are in the wrong order, it swaps them and
moves one step back. Otherwise it moves one step forward.

Time Complexity:  O(n^2) in the worst case
Space Complexity: O(1)

Reference: https://en.wikipedia.org/wiki/Gnome_sort
"""


def gnome_sort(lst: list) -> list:
    """
    Pure implementation of the gnome sort algorithm in Python

    Take some mutable ordered collection with heterogeneous comparable items inside as
    arguments, return the same collection ordered by ascending.

    Examples:
    >>> gnome_sort([0, 5, 3, 2, 2])
    [0, 2, 2, 3, 5]

    >>> gnome_sort([])
    []

    >>> gnome_sort([-2, -5, -45])
    [-45, -5, -2]

    >>> "".join(gnome_sort(list(set("Gnomes are stupid!"))))
    ' !Gadeimnoprstu'
    """
    if len(lst) <= 1:
        return lst

    i = 1

    while i < len(lst):
        if lst[i - 1] <= lst[i]:
            i += 1
        else:
            lst[i - 1], lst[i] = lst[i], lst[i - 1]
            i -= 1
            if i == 0:
                i = 1

    return lst


if __name__ == "__main__":
    user_input = input("Enter numbers separated by a comma:\n").strip()
    unsorted = [int(item) for item in user_input.split(",")]
    print(gnome_sort(unsorted))