Problem:
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?
思路：
Solution (C++):
bool isPowerOfThree(int n) {
if (n <= 0) return false;
while (n%3 == 0) n /= 3;
if (n == 1) return true;
return false;
}
性能：
Runtime: 40 ms Memory Usage: 5.8 MB
思路：
Solution (C++):
性能：
Runtime: ms Memory Usage: MB
