{leetcode}/problems/power-of-three/[LeetCode - Power of Three^]
发现一个很奇怪的问题：如果通过计算相乘来判断，则会超时；如果通过相除来判断，则能顺利通过。感觉计算量是一样的啊？为什会有这么大的差距啊？
利用对数计算也不失为一个很好的办法！
Given an integer, write a function to determine if it is a power of three.
Example 1:
Input: 27 Output: true
Example 2:
Input: 0 Output: false
Example 3:
Input: 9 Output: true
Example 4:
Input: 45 Output: false
Follow up:
Could you do it without using any loop / recursion?
link:{sourcedir}/_0326_PowerOfThree.java[role=include]