Python/bit_manipulation/is_power_of_two.py

58 lines
1.3 KiB
Python
Raw Normal View History

"""
Author : Alexander Pantyukhin
Date : November 1, 2022
Task:
Given a positive int number. Return True if this number is power of 2
or False otherwise.
Implementation notes: Use bit manipulation.
For example if the number is the power of two it's bits representation:
n = 0..100..00
n - 1 = 0..011..11
n & (n - 1) - no intersections = 0
"""
def is_power_of_two(number: int) -> bool:
"""
Return True if this number is power of 2 or False otherwise.
>>> is_power_of_two(0)
True
>>> is_power_of_two(1)
True
>>> is_power_of_two(2)
True
>>> is_power_of_two(4)
True
>>> is_power_of_two(6)
False
>>> is_power_of_two(8)
True
>>> is_power_of_two(17)
False
>>> is_power_of_two(-1)
Traceback (most recent call last):
...
ValueError: number must not be negative
>>> is_power_of_two(1.2)
Traceback (most recent call last):
...
TypeError: unsupported operand type(s) for &: 'float' and 'float'
# Test all powers of 2 from 0 to 10,000
>>> all(is_power_of_two(int(2 ** i)) for i in range(10000))
True
"""
if number < 0:
raise ValueError("number must not be negative")
return number & (number - 1) == 0
if __name__ == "__main__":
import doctest
doctest.testmod()