50. Pow(x, n) Leetcode Java

Implement pow(x, n).
Solution:
Basically, it is a math problem.
if n is even pow(x,n) =pow(x,n/2) * pow(x,n/2);
if n is odd, a) if n is positive pow(x,n)=pow(x,n/2) * pow(x,n/2) * x;
             b) if n is negative pow(x,n)=pow(x,n/2) * pow(x,n/2) /x;

 public double pow(double x, int n) {  
    if (n == 0) return 1.0;  
    double half = pow(x, n/2);  
    if (n%2 == 0) return half*half;  
    else if (n>0) return half*half*x;  
    else return half/x*half;  
   }