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75 lines
1.8 KiB
Python
75 lines
1.8 KiB
Python
"""
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A recursive implementation of the insertion sort algorithm
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"""
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from __future__ import annotations
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def rec_insertion_sort(collection: list, n: int):
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"""
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Given a collection of numbers and its length, sorts the collections
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in ascending order
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:param collection: A mutable collection of comparable elements
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:param n: The length of collections
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>>> col = [1, 2, 1]
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>>> rec_insertion_sort(col, len(col))
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>>> print(col)
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[1, 1, 2]
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>>> col = [2, 1, 0, -1, -2]
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>>> rec_insertion_sort(col, len(col))
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>>> print(col)
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[-2, -1, 0, 1, 2]
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>>> col = [1]
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>>> rec_insertion_sort(col, len(col))
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>>> print(col)
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[1]
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"""
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# Checks if the entire collection has been sorted
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if len(collection) <= 1 or n <= 1:
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return
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insert_next(collection, n - 1)
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rec_insertion_sort(collection, n - 1)
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def insert_next(collection: list, index: int):
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"""
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Inserts the '(index-1)th' element into place
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>>> col = [3, 2, 4, 2]
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>>> insert_next(col, 1)
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>>> print(col)
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[2, 3, 4, 2]
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>>> col = [3, 2, 3]
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>>> insert_next(col, 2)
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>>> print(col)
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[3, 2, 3]
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>>> col = []
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>>> insert_next(col, 1)
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>>> print(col)
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[]
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"""
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# Checks order between adjacent elements
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if index >= len(collection) or collection[index - 1] <= collection[index]:
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return
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# Swaps adjacent elements since they are not in ascending order
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collection[index - 1], collection[index] = (
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collection[index],
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collection[index - 1],
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)
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insert_next(collection, index + 1)
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if __name__ == "__main__":
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numbers = input("Enter integers separated by spaces: ")
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number_list: list[int] = [int(num) for num in numbers.split()]
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rec_insertion_sort(number_list, len(number_list))
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print(number_list)
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