342. Power of Four-4的幂

Given an integer n, return true if it is a power of four. Otherwise, return false.

An integer n is a power of four, if there exists an integer x such that n == 4x.

Example 1:
Input: n = 16
Output: true

Example 2:
Input: n = 5
Output: false

Example 3:
Input: n = 1
Output: true

Constraints:

• -2^31 <= n <= 2^31 - 1

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

class Solution:
    def isPowerOfFour(self, n: int) -> bool:
        if n <= 0:
            return False
        while n > 1:
            if n%4 == 0:
                n //= 4
                continue 
            else:
                return False
        return True