326. Power of Three

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?

javascript：

/**
* @param {number} n
* @return {boolean}
*/
var isPowerOfThree = function(n) {
var num=Math.log(n)/Math.log(3);
var num1=Math.abs(num-Math.round(num));
if(num1<=0.00000000001)
{
return true;
}
else return false;
};