TheAlgorithms-Python

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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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