题目描述：

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?

代码实现：

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