Pow(x, n)

Implement pow(x, n).

public class Solution {    public double pow(double x, int n) {        //判断x是不是0        if(Math.abs(x-0)<0.0000001)            return 1;        //指数为负数        if(n<0){            return 1/p(x,-((long)n));        }        if(n==0)            return 1;        return p(x,n);            }        public double p(double x,long n){        if(n==0)            return 1;        if(n==1)            return x;        if(n%2==0){            double r=p(x,n/2);            return r*r;        }        double r=p(x,(n-1)/2);        return r*r*x;    }}