326. Power of Three | Keep Walking

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?

递归和循环的做法很简单，就是不停的除以3，直到不能整除，结果是1的话，就是3的指数，否则则不是。
但是这个题目的follow up不让用循环和递归。

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public boolean isPowerOfThree(int n) {
    return n > 0 && (n == 1 || (n % 3 == 0 && isPowerOfThree(n / 3)));
}

public boolean isPowerOfThree(int n) {
    if (n > 1)
        while (n % 3 == 0) n /= 3;
    return n == 1;
}