LC342 Power of Four

class Solution:
    def isPowerOfFour(self, num: int) -> bool:
        # time O(N/4)
        if num <= 0 :
            return False
        power = 0
        x = 0
        while x < num :
            x = 4**power
            if x == num:
                return True 
            power += 1
        return False

class Solution:
# main idea: num is power of 2 and binary form '1' at odd position; big condition:  num >0 
    def isPowerOfFour(self, num: int) -> bool:
        return num > 0 and num & (num-1)==0 and ((num & 0x55555555) == num)