题目：

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?

链接：

3/7/2017

不满足题目的解法，注意n == 1也是true

1 public class Solution {2     public boolean isPowerOfThree(int n) {3         if (n == 1) return true;4         if (n == 2) return false;5         while (n > 3 && n % 3 == 0) n /= 3;6         if (n == 3) return true;7         return false;8     }9 }

可以简化为

1 public class Solution { 2     public boolean isPowerOfThree(int n) { 3         if (n < 1) { 4             return false; 5         } 6  7         while (n % 3 == 0) { 8             n /= 3; 9         }10 11         return n == 1;12     }13 }

题目给出的4种解法，然而并不觉得比native解法好到哪里去。