Pow(x, n)

Implement pow(x, n).
Tips:
1. Use divide and conquer.
2. Powers can be negative. Always remember this.
3. Try to reduce the times of multiplication as many as possible.

01 public double pow(double x, int n) {
02     if(n==0)
03         return 1;
04     if(n==1)
05         return x;
06   
07     boolean isNegative=false;
08     if(n<0)
09     {
10         n=-n;
11         isNegative=true;
12     }
13   
14     double result=pow(x,n/2);
15     result=result*result;
16     if(n%2==1)
17         result*=x;
18     if(isNegative)
19         result=1/result;
20     return result;
21 }