text: '''
  Created on 2016年4月21日
  
  @author: Darren
  '''
  '''
  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?
  '''
  def isPowerOfFour(num):
      """
      :type num: int
      :rtype: bool
      """
      return num > 0 and (num&(num-1)) == 0 and (num & 0x55555555) != 0
  
  print(isPowerOfFour(64))