231. Power of Two

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

Example 1:

Input: 1 Output: true Explanation: 20 = 1 Example 2:

Input: 16 Output: true Explanation: 24 = 16 Example 3:

Input: 218 Output: false

思路：位运算& 如果给定num为2的n次方的话，num&(num-1)必不为0 代码：python3

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        if n<=0:
            return False
        else:
            return not n&(n-1)