Power of Two

Question

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

Tags

• Mathematics

Thought

Two solutions

• while loop
• binary number

For the first one, we can use a while loop to divide the number by 2 until it cannot be divided by 2.

For the second one, we can count the number of 1 in the corresponding binary number. If the number is exactly 1, then it is the pow of 2.

Code

while loop

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

binary number

class Solution(object):
    def isPowerOfTwo(self, n):
        """
        :type n: int
        :rtype: bool
        """
        if n <= 0:
            return False
        num = bin(n).count('1')
        return num == 1