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57 lines
1.5 KiB
Python
57 lines
1.5 KiB
Python
"""
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This is a pure python implementation of the merge sort algorithm
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For doctests run following command:
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python -m doctest -v merge_sort.py
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or
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python3 -m doctest -v merge_sort.py
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For manual testing run:
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python merge_sort.py
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"""
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from __future__ import print_function
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def merge_sort(collection):
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"""Pure implementation of the merge sort algorithm in Python
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:param collection: some mutable ordered collection with heterogeneous
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comparable items inside
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:return: the same collection ordered by ascending
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Examples:
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>>> merge_sort([0, 5, 3, 2, 2])
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[0, 2, 2, 3, 5]
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>>> merge_sort([])
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[]
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>>> merge_sort([-2, -5, -45])
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[-45, -5, -2]
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"""
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def merge(left, right):
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'''merge left and right
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:param left: left collection
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:param right: right collection
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:return: merge result
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'''
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result = []
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while left and right:
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result.append(left.pop(0) if left[0] <= right[0] else right.pop(0))
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return result + left + right
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if len(collection) <= 1:
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return collection
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mid = len(collection) // 2
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return merge(merge_sort(collection[:mid]), merge_sort(collection[mid:]))
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if __name__ == '__main__':
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try:
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raw_input # Python 2
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except NameError:
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raw_input = input # Python 3
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user_input = raw_input('Enter numbers separated by a comma:\n').strip()
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unsorted = [int(item) for item in user_input.split(',')]
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print(*merge_sort(unsorted), sep=',')
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