Power of Four 

Topic : Recursion

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 == 4x.

    bool isPowerOfFour(int n) {
        if(n<=0) return false;
        if(n==1 || n==4) return true;
        if(n%4 !=0) return false;
        return isPowerOfFour(n/4);
    }

public boolean isPowerOfFour(int n) {
    return n > 1 && n %4 == 0 ? isPowerOfFour(n/4) : n == 1;
}

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

Wondering :

class Solution: def isPowerOfFour(self, n: int) -> bool: return n > 0 and log2(n) % 2 == 0