Power of Three--imcomplete

/*
LeetCode 326:
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?


Solution:
Language: C++
Tag: 
*/

class Solution {
public:
    bool isPowerOfThree(int n) {
        if (n <= 0) {
            return false;
        }
        /*
        // 1. loop
        while (n != 1) {
            if (n % 3 != 0) {
                return false;
            }
            n /= 3;
        }
        return true;
        */
        
        /*
        // 2. recursion
        if (n == 1) {
            return true;
        }
        if (n % 3 != 0) {
            return false;
        }
        return isPowerOfThree(n / 3);
        */
        
        // 3. without loop or recursion -- base conversion??
        
        
        // 4. log formula
        
        
        // 5. limitation
    }
};