50. Pow(x, n)

class Solution {
    public double myPow(double x, int n) {
        double res = 1.0;
        long N = n;
        
        if (n < 0) {
            x = 1 / x;
            N = -N; // wrong: N = -n;
        }
        
        double curProduct = x;
        for (long i = N; i > 0; i /= 2) {
            if (i % 2 == 1) {
                res *= curProduct;
            }
            
            curProduct *= curProduct;
        }
        
        return res;
    }
}