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62 lines
1.7 KiB
Python
62 lines
1.7 KiB
Python
"""
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Author : Syed Faizan (3rd Year Student IIIT Pune)
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github : faizan2700
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You are given a bitmask m and you want to efficiently iterate through all of
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its submasks. The mask s is submask of m if only bits that were included in
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bitmask are set
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"""
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from typing import List
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def list_of_submasks(mask: int) -> List[int]:
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"""
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Args:
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mask : number which shows mask ( always integer > 0, zero does not have any
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submasks )
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Returns:
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all_submasks : the list of submasks of mask (mask s is called submask of mask
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m if only bits that were included in original mask are set
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Raises:
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AssertionError: mask not positive integer
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>>> list_of_submasks(15)
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[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
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>>> list_of_submasks(13)
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[13, 12, 9, 8, 5, 4, 1]
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>>> list_of_submasks(-7) # doctest: +ELLIPSIS
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Traceback (most recent call last):
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...
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AssertionError: mask needs to be positive integer, your input -7
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>>> list_of_submasks(0) # doctest: +ELLIPSIS
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Traceback (most recent call last):
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...
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AssertionError: mask needs to be positive integer, your input 0
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"""
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fmt = "mask needs to be positive integer, your input {}"
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assert isinstance(mask, int) and mask > 0, fmt.format(mask)
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"""
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first submask iterated will be mask itself then operation will be performed
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to get other submasks till we reach empty submask that is zero ( zero is not
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included in final submasks list )
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"""
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all_submasks = []
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submask = mask
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while submask:
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all_submasks.append(submask)
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submask = (submask - 1) & mask
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return all_submasks
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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