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iterating_through_submasks is added with doctests

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faizan2700 2019-12-18 10:27:19 +05:30
parent 6e484d8e7c
commit 00351ca899
1 changed files with 22 additions and 9 deletions
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dynamic_programming/iterating_through_submasks.py
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@ -1,10 +1,13 @@
''' """
Author : Syed Faizan (3rd Year Student IIIT Pune)
github : faizan2700
You are given a bitmask m and you want to efficiently iterate through all of You are given a bitmask m and you want to efficiently iterate through all of
its submasks. The mask s is submask of m if only bits that were included in its submasks. The mask s is submask of m if only bits that were included in
bitmask are set bitmask are set
''' """
def list_of_submasks(mask)->list:
def list_of_submasks(mask) -> list:
""" """
Args: Args:
@ -21,26 +24,36 @@ def list_of_submasks(mask)->list:
[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1] [15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
>>> list_of_submasks(13) >>> list_of_submasks(13)
[13, 12, 9, 8, 5, 4, 1] [13, 12, 9, 8, 5, 4, 1]
>>> list_of_submasks(-7) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
AssertionError: mask needs to be positive integer, your input -7
>>> list_of_submasks(0) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
AssertionError: mask needs to be positive integer, your input 0
""" """
fmt = "n needs to be positive integer, your input {}" fmt = "n needs to be positive integer, your input {}"
assert isinstance(mask, int) and mask > 0, fmt.format(mask) assert isinstance(mask, int) and mask > 0, fmt.format(mask)
''' """
first submask iterated will be mask itself then operation will be performed first submask iterated will be mask itself then operation will be performed
to get other submasks till we reach empty submask that is zero ( zero is not to get other submasks till we reach empty submask that is zero ( zero is not
included in final submasks list ) included in final submasks list )
''' """
all_submasks = [] all_submasks = []
submask = mask submask = mask
while submask: while submask:
all_submasks.append(submask) all_submasks.append(submask)
submask = (submask-1) & mask submask = (submask - 1) & mask
return all_submasks return all_submasks
if __name__ == '__main__':
if __name__ == "__main__":
import doctest import doctest
doctest.testmod() doctest.testmod()