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power-of-four.py
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31 lines (27 loc) · 747 Bytes
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# Time: O(1)
# Space: O(1)
# Given an integer (signed 32 bits), write a function to check whether it is a power of 4.
#
# Example:
# Given num = 16, return true. Given num = 5, return false.
#
# Follow up: Could you solve it without loops/recursion?
class Solution(object):
def isPowerOfFour(self, num):
"""
:type num: int
:rtype: bool
"""
return num > 0 and (num & (num - 1)) == 0 and \
((num & 0b01010101010101010101010101010101) == num)
# Time: O(1)
# Space: O(1)
class Solution2(object):
def isPowerOfFour(self, num):
"""
:type num: int
:rtype: bool
"""
while num and not (num & 0b11):
num >>= 2
return (num == 1)