Power(x, n)

Calculate nth power of a double number x, where n is an integer. You must handle cases that:

1. x is negative
2. n is negative
3. x = 1 and n = Integer.MAX_VALUE
4. x = 1 and n = Integer.MIN_VALUE
5. x = -1 and n = Integer.MAX_VALUE
6. x = -1 and n = Integer.MIN_VALUE

As for x = 1 we directly return 1. For x < 0 we find the result's sign first and calculate -x's power of n. For n < 0, we calculate 1/pow(x, -n).

public class Power {
    public double myPow(double x, int n) {
        if (x == 0) return 0;
        if (x == 1) return 1.0;
        if (x < 0) return ((n & 1) == 1) ? -myPow(-x, n) : myPow(-x, n);
        else if (n == 0) return 1;
        else if (n < 0) return 1.0 / myPow(x, -n);
        else if ((n & 1) == 1) return myPow(x, n - 1) * x;
        else {
            double r = myPow(x, n >> 1);
            return r * r;
        }
    }
}