Swift算法10-Power of x

Implement pow(x, n).

class Solution {
    func power(var x: Double, var _ n: Int) -> Double {
        if x == 0 {return 0}
        if n == 0 {return 1}
        if n < 0 {
            n = -n
            x = 1/x
        }
        
        
        return (n%2 == 0) ? power(x*x, n/2) : power(x*x, n/2) * x
    }
}