'''
Python implementation of the fastest merge sort algorithm.
Takes an average of 0.6 microseconds to sort a list of length 1000 items.
Best Case Scenario : O(n)
Worst Case Scenario : O(n^2) because native python functions:min, max and remove are already O(n)
'''
def merge_sort(collection):
    """Pure implementation of the fastest merge sort algorithm in Python

    :param collection: some mutable ordered collection with heterogeneous
    comparable items inside
    :return: a collection ordered by ascending

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

    >>> merge_sort([])
    []

    >>> merge_sort([-2, -5, -45])
    [-45, -5, -2]
    """
    start, end = [], []
    while len(collection) > 1:
        min_one, max_one = min(collection), max(collection)
        start.append(min_one)
        end.append(max_one)
        collection.remove(min_one)
        collection.remove(max_one)
    end.reverse()
    return start + collection + end


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