LEET code -- 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?


如果不用loop

class Solution(object):
    def isPowerOfThree(self, n):
        # 1162261467=3^19. 3^20 is bigger than int.
        return n > 0 and 1162261467 % n == 0

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bool isPowerOfThree(int n) { if(n<=0)return false; while(n%3==0)n/=3; return n==1? true:false; }