Power of 3

Question

不用任何Loop和recursion，check一个number是否是3的power

Thoughts

This can be generalized for any prime number.

Let's say we have 2 number m & n

if m is a power of n then for any number p.
    1. For all p <= m
    2. m % p == 0 if and only if p is also a power of n

而最大的32bit signed interger是1162261467

Solution

class Solution(object):
    def isPowerOfThree(self, n):
        """
        :type n: int
        :rtype: bool
        """
        return (n > 0) and (1162261467 % n == 0)

Reference