class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) return false;            // Zero and negative numbers are false.
        if (n == 1) return true;             // One is 2^0, so that's true.
        if ((n%2) == 1) return false;        // Any odd number is not a power of two.
        return isPowerOfTwo(n/2);            // If it's even, try dividing it by two.
    }
};