TheAlgorithms-Python

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def aliquot_sum(input_num: int) -> int:
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    """
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    Finds the aliquot sum of an input integer, where the
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    aliquot sum of a number n is defined as the sum of all
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    natural numbers less than n that divide n evenly. For
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    example, the aliquot sum of 15 is 1 + 3 + 5 = 9. This is
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    a simple O(n) implementation.
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    @param input_num: a positive integer whose aliquot sum is to be found
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    @return: the aliquot sum of input_num, if input_num is positive.
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    Otherwise, raise a ValueError
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    Wikipedia Explanation: https://en.wikipedia.org/wiki/Aliquot_sum
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    >>> aliquot_sum(15)
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    9
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    >>> aliquot_sum(6)
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    6
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    >>> aliquot_sum(-1)
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    Traceback (most recent call last):
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      ...
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    ValueError: Input must be positive
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    >>> aliquot_sum(0)
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    Traceback (most recent call last):
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      ...
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    ValueError: Input must be positive
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    >>> aliquot_sum(1.6)
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    Traceback (most recent call last):
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      ...
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    ValueError: Input must be an integer
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    >>> aliquot_sum(12)
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    16
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    >>> aliquot_sum(1)
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    0
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    >>> aliquot_sum(19)
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    1
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    """
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    if not isinstance(input_num, int):
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        raise ValueError("Input must be an integer")
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    if input_num <= 0:
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        raise ValueError("Input must be positive")
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    return sum(
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        divisor for divisor in range(1, input_num // 2 + 1) if input_num % divisor == 0
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    )
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if __name__ == "__main__":
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    import doctest
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    doctest.testmod()
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