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UTSAV SINGHALpre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>Christian Clauss* feat(arrays): Add in-place array reversal algorithm * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Enhance docstring for reverse_array function Updated docstring to clarify that the function returns the reversed list. * Clarify return value in reverse_array function Updated docstring to clarify that the function returns the reversed list. Modified example usage to display the reversed array correctly. --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss <cclauss@me.com>
73 lines
2.1 KiB
Python
73 lines
2.1 KiB
Python
"""
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In-place array reversal that also returns the reversed list to the caller.
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This algorithm reverses the elements of a list without using extra space.
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"""
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from typing import Any
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def reverse_array(arr: list[Any]) -> list[Any]:
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"""
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Reverses a list in-place.
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This function takes a list and reverses its elements using a two-pointer
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approach. The left pointer starts at the beginning of the list, and the
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right pointer starts at the end. The elements at these two pointers are
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swapped, and the pointers move towards the center until they meet or cross.
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Args:
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arr: The list to be reversed.
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Returns:
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The same list, now reversed. This allows for method chaining.
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Doctests:
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>>> reverse_array([1, 2, 3, 4, 5])
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[5, 4, 3, 2, 1]
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>>> reverse_array(['a', 'b', 'c', 'd'])
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['d', 'c', 'b', 'a']
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>>> reverse_array([10.5, 20.2, 30.8])
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[30.8, 20.2, 10.5]
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>>> reverse_array(["apple", "banana", "cherry"])
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['cherry', 'banana', 'apple']
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>>> reverse_array([1])
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[1]
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>>> reverse_array([])
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[]
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>>> reverse_array(list(range(5)))
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[4, 3, 2, 1, 0]
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>>> reverse_array(tuple(range(5)))
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Traceback (most recent call last):
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...
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TypeError: 'tuple' object does not support item assignment
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>>> reverse_array(range(5))
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Traceback (most recent call last):
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...
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TypeError: 'range' object does not support item assignment
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"""
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left = 0
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right = len(arr) - 1
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while left < right:
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# Swap the elements at the left and right pointers
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arr[left], arr[right] = arr[right], arr[left]
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# Move the pointers towards the center
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left += 1
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right -= 1
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return arr
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if __name__ == "__main__":
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# The doctest module runs the tests embedded in the function's docstring.
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# To run the tests, execute this script from the command line:
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# python -m doctest -v reverse_array.py
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import doctest
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doctest.testmod()
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# Example usage:
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print("\n--- Example Usage ---")
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sample_array = [10, 20, 30, 40, 50, 60]
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print(f"{sample_array = }")
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print(f"{reverse_array(sample_array) = }")
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