Problem description:

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example 1:

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Input: 16
Output: true

Example 2:

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Input: 5
Output: false

Solution:

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class Solution:
    def isPowerOfFour(self, num: int) -> bool:
        while num > 0 and num%4 == 0:
            num/= 4
        return num == 1

time complexity: $O(n)$
space complexity: $O(1)$
reference:
related problem: