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a25c53e8b0
* Fix argument validation for count_1s_brian_kernighan_method
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
47 lines
1.3 KiB
Python
47 lines
1.3 KiB
Python
def get_1s_count(number: int) -> int:
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"""
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Count the number of set bits in a 32 bit integer using Brian Kernighan's way.
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Ref - https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan
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>>> get_1s_count(25)
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3
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>>> get_1s_count(37)
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3
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>>> get_1s_count(21)
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3
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>>> get_1s_count(58)
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4
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>>> get_1s_count(0)
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0
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>>> get_1s_count(256)
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1
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>>> get_1s_count(-1)
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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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>>> get_1s_count(0.8)
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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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>>> get_1s_count("25")
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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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count = 0
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while number:
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# This way we arrive at next set bit (next 1) instead of looping
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# through each bit and checking for 1s hence the
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# loop won't run 32 times it will only run the number of `1` times
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number &= number - 1
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count += 1
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return count
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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