LeetCode-342(4的幂)

v1

• 递归

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

v2

• 迭代 一直对4取余 直到为0

Pass

v3

• 官方题解4 先判断是否为2的幂 再对3取模余1的数为4的幂

class Solution:
    def isPowerOfFour(self, n: int) -> bool:
        """ 题解4方法 """
        return n > 0 and n & (n-1) == 0 and n % 3 == 1