Power of Two

题目：

Given an integer, write a function to determine if it is a power of two.

解题思路：

class Solution:
    # @param {integer} n
    # @return {boolean}
    def isPowerOfTwo(self, n):
        if n<=0:
            return False
        while n>=2:
            if n%2!=0:
                return False
            n = n/2
        return True