mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-24 05:21:09 +00:00
44 lines
1.2 KiB
Python
44 lines
1.2 KiB
Python
def get_1s_count(number: int) -> int:
|
|
"""
|
|
Count the number of set bits in a 32 bit integer using Brian Kernighan's way.
|
|
Ref - https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan
|
|
>>> get_1s_count(25)
|
|
3
|
|
>>> get_1s_count(37)
|
|
3
|
|
>>> get_1s_count(21)
|
|
3
|
|
>>> get_1s_count(58)
|
|
4
|
|
>>> get_1s_count(0)
|
|
0
|
|
>>> get_1s_count(256)
|
|
1
|
|
>>> get_1s_count(-1)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: the value of input must be positive
|
|
>>> get_1s_count(0.8)
|
|
Traceback (most recent call last):
|
|
...
|
|
TypeError: Input value must be an 'int' type
|
|
"""
|
|
if number < 0:
|
|
raise ValueError("the value of input must be positive")
|
|
elif isinstance(number, float):
|
|
raise TypeError("Input value must be an 'int' type")
|
|
count = 0
|
|
while number:
|
|
# This way we arrive at next set bit (next 1) instead of looping
|
|
# through each bit and checking for 1s hence the
|
|
# loop won't run 32 times it will only run the number of `1` times
|
|
number &= number - 1
|
|
count += 1
|
|
return count
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|