LeetCode342. 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?

class Solution {  
public:  
    bool isPowerOfFour(int num) {  
        bool is=true;  
        if(num==0) is=false;  
        else if(num==1) is=true;  
        else if(num%4!=0) is=false;  
        else if(num%4==0) is=isPowerOfFour(num/4);  
        return is;  
    }  
};