Question

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example:

Given num = 16, return true. Given num = 5, return false.

Follow up: Could you solve it without loops/recursion?

Solution

import re

class Solution(object):
    def isPowerOfFour(self, num):
        """
        :type num: int
        :rtype: bool
        """
        if num <= 0:
            return False
        elif num == 1:
            return True
        else:
            num = "{0:b}".format(num)
            return re.match("^10+$", num) is not None and len(num[1:]) % 2 == 0