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* Create find_previous_power_of_two.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Update find_previous_power_of_two.py This change avoids the unnecessary left shift operation * Update find_previous_power_of_two.py --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss <cclauss@me.com>
31 lines
967 B
Python
31 lines
967 B
Python
def find_previous_power_of_two(number: int) -> int:
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"""
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Find the largest power of two that is less than or equal to a given integer.
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https://stackoverflow.com/questions/1322510
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>>> [find_previous_power_of_two(i) for i in range(18)]
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[0, 1, 2, 2, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16, 16]
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>>> find_previous_power_of_two(-5)
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Traceback (most recent call last):
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...
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ValueError: Input must be a non-negative integer
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>>> find_previous_power_of_two(10.5)
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Traceback (most recent call last):
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...
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ValueError: Input must be a non-negative integer
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"""
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if not isinstance(number, int) or number < 0:
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raise ValueError("Input must be a non-negative integer")
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if number == 0:
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return 0
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power = 1
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while power <= number:
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power <<= 1 # Equivalent to multiplying by 2
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return power >> 1 if number > 1 else 1
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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