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?
Credits:Special thanks to @yukuairoy  for adding this problem and creating all test cases.
class Solution:
     def isPowerOfFour(self, num):
         """
         :type num: int
         :rtype: bool
         """
         if num == 1:
             return True
 
         target = 1
         while target < num:
             target *= 4
             if target == num:
                 return True
 
         return False
class Solution:
     def isPowerOfFour(self, num):
         """
         :type num: int
         :rtype: bool
         """
         if num == 1:
             return True
 
         target = 1
         while target < num:
             target *= 4
             if target == num:
                 return True
 
         return False