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Added largest_pow_of_two_le_num #9374

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60 changes: 60 additions & 0 deletions bit_manipulation/largest_pow_of_two_le_num.py
Original file line number Diff line number Diff line change
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"""
Author : Naman Sharma
Date : October 2, 2023

Task:
To Find the largest power of 2 less than or equal to a given number.

Implementation notes: Use bit manipulation.
We start from 1 & left shift the set bit to check if (res<<1)<=number.
Each left bit shift represents a pow of 2.

For example:
number: 15
res: 1 0b1
2 0b10
4 0b100
8 0b1000
16 0b10000 (Exit)
"""


def largest_pow_of_two_le_num(number: int) -> int:
"""
Return the largest power of two less than or equal to a number.

>>> largest_pow_of_two_le_num(0)
0
>>> largest_pow_of_two_le_num(1)
1
>>> largest_pow_of_two_le_num(-1)
0
>>> largest_pow_of_two_le_num(3)
2
>>> largest_pow_of_two_le_num(15)
8
>>> largest_pow_of_two_le_num(99)
64
>>> largest_pow_of_two_le_num(178)
128
>>> largest_pow_of_two_le_num(999999)
524288
>>> largest_pow_of_two_le_num(99.9)
Traceback (most recent call last):
...
TypeError: Input value must be a 'int' type
"""
if isinstance(number, float):
raise TypeError("Input value must be a 'int' type")
if number <= 0:
return 0
res = 1
while (res << 1) <= number:
res <<= 1
return res


if __name__ == "__main__":
import doctest

doctest.testmod()