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merge_sort.py
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merge_sort.py
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"""
This is a pure Python implementation of the merge sort algorithm.
For doctests run following command:
python -m doctest -v merge_sort.py
or
python3 -m doctest -v merge_sort.py
For manual testing run:
python merge_sort.py
"""
def merge_sort(collection: list) -> list:
"""
Sorts a list using the merge sort algorithm.
:param collection: A mutable ordered collection with comparable items.
:return: The same collection ordered in ascending order.
Time Complexity: O(n log n)
Examples:
>>> merge_sort([0, 5, 3, 2, 2])
[0, 2, 2, 3, 5]
>>> merge_sort([])
[]
>>> merge_sort([-2, -5, -45])
[-45, -5, -2]
"""
def merge(left: list, right: list) -> list:
"""
Merge two sorted lists into a single sorted list.
:param left: Left collection
:param right: Right collection
:return: Merged result
"""
result = []
while left and right:
result.append(left.pop(0) if left[0] <= right[0] else right.pop(0))
result.extend(left)
result.extend(right)
return result
if len(collection) <= 1:
return collection
mid_index = len(collection) // 2
return merge(merge_sort(collection[:mid_index]), merge_sort(collection[mid_index:]))
if __name__ == "__main__":
import doctest
doctest.testmod()
try:
user_input = input("Enter numbers separated by a comma:\n").strip()
unsorted = [int(item) for item in user_input.split(",")]
sorted_list = merge_sort(unsorted)
print(*sorted_list, sep=",")
except ValueError:
print("Invalid input. Please enter valid integers separated by commas.")