power-of-two.py

# Time:  O(1)
# Space: O(1)
#
# Given an integer, write a function to determine if it is a power of two.
#

class Solution:
    # @param {integer} n
    # @return {boolean}
    def isPowerOfTwo(self, n):
        return n > 0 and (n & (n - 1)) == 0

class Solution2:
    # @param {integer} n
    # @return {boolean}
    def isPowerOfTwo(self, n):
        return n > 0 and (n & ~-n) == 0