判断一个数是不是3的幂——Power of three?

Given an integer, write a function to determine if it is a power of three.

Follow up:

Could you do it without using any loop / recursion?
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Python:

solution 1:

class Solution(object):
def isPowerOfThree(self, n):
"""
:type n: int
:rtype: bool
"""
return n > 0 and 3 ** round(math.log(n,3)) == n
solution 2:



class Solution(object):
def isPowerOfThree(self, n):
"""
:type n: int
:rtype: bool
"""
if n == 1:
return True
if n == 0 or n % 3 > 0:
return False
return self.isPowerOfThree(n / 3)