TheAlgorithms-Python

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# Information on 2's complement: https://en.wikipedia.org/wiki/Two%27s_complement
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def twos_complement(number: int) -> str:
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    """
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    Take in a negative integer 'number'.
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    Return the two's complement representation of 'number'.
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    >>> twos_complement(0)
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    '0b0'
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    >>> twos_complement(-1)
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    '0b11'
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    >>> twos_complement(-5)
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    '0b1011'
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    >>> twos_complement(-17)
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    '0b101111'
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    >>> twos_complement(-207)
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    '0b100110001'
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    >>> twos_complement(1)
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    Traceback (most recent call last):
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        ...
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    ValueError: input must be a negative integer
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    """
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    if number > 0:
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        raise ValueError("input must be a negative integer")
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    binary_number_length = len(bin(number)[3:])
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    twos_complement_number = bin(abs(number) - (1 << binary_number_length))[3:]
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    twos_complement_number = (
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        (
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            "1"
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            + "0" * (binary_number_length - len(twos_complement_number))
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            + twos_complement_number
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        )
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        if number < 0
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        else "0"
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    )
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    return "0b" + twos_complement_number
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if __name__ == "__main__":
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    import doctest
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    doctest.testmod()
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