Leetcode 342. Power of Four

Problem

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 = = 4 x n == 4^x n==4x.

Algorithm

Use the bit operations.

Code

class Solution:
    def isPowerOfFour(self, n: int) -> bool:
        '''
        if n <= 0:
            return False
        m = int(log(n)/log(4))
        return 4 ** m == n
        '''
        if n <= 0:
            return False
        while n > 1:
            if n & 3 != 0:
                return False
            n >>= 2
        return True