Power_of_Two.md

231. Power of Two

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

Method:

recursion:

class Solution(object):
    def isPowerOfTwo(self, n):
        """
        :type n: int
        :rtype: bool
        """
        if n==1:
            return True
        if n%2 or n<=0:
            return False
        return self.isPowerOfTwo(n/2)

iteration:

class Solution(object):
    def isPowerOfTwo(self, n):
        """
        :type n: int
        :rtype: bool
        """
        while n>0:
            if n==1:
                return True
            if n%2:
                return False
            n/=2
        return False

Solution:

bit manipulation:

class Solution(object):
    def isPowerOfTwo(self, n):
        """
        :type n: int
        :rtype: bool
        """
        if n<=0:
            return False
        return n & (n-1)==0