mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-05 02:40:16 +00:00
8217f9bd35
* Create find_previous_power_of_two.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Update find_previous_power_of_two.py This change avoids the unnecessary left shift operation * Update find_previous_power_of_two.py --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss <cclauss@me.com>
31 lines
967 B
Python
31 lines
967 B
Python
def find_previous_power_of_two(number: int) -> int:
|
|
"""
|
|
Find the largest power of two that is less than or equal to a given integer.
|
|
https://stackoverflow.com/questions/1322510
|
|
|
|
>>> [find_previous_power_of_two(i) for i in range(18)]
|
|
[0, 1, 2, 2, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16, 16]
|
|
>>> find_previous_power_of_two(-5)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: Input must be a non-negative integer
|
|
>>> find_previous_power_of_two(10.5)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: Input must be a non-negative integer
|
|
"""
|
|
if not isinstance(number, int) or number < 0:
|
|
raise ValueError("Input must be a non-negative integer")
|
|
if number == 0:
|
|
return 0
|
|
power = 1
|
|
while power <= number:
|
|
power <<= 1 # Equivalent to multiplying by 2
|
|
return power >> 1 if number > 1 else 1
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|