LeetCode - Power of Four

Question

Link : https://leetcode.com/problems/power-of-four/

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

Example:
Given num = 16, return true. Given num = 5, return false.

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

Code

直接上一个非递归/非循环版本的，之前有个是判断一个数是不是3的幂，和这个是有异曲同工之妙的。（C++ : 9ms）

class Solution {
public:
    bool isPowerOfFour(int num) {
        if(num == 0)
            return false;
        return pow(4, int(log(num) / log(4))) == num;
    }
};