leetcode power(x,n)

class Solution {
public:
    double pow(double x, int n)
    {
        double a=1;
        if(n==0)return 1;
        if(x==1)return 1;
        if(x==-1)
        {
            if(n&1)return -1;
            else return 1;
        }
        int absn=abs(n);
        a=power(x,absn);
        if(n<0)
        {
            a=1/a;
        }
        return a;
    }
    double power(double x,int n)
    {
        double result=1;
        if(n==1)return x;
        if(n&1)
        {
          result*=x;
          n=n-1;
        }
        double temp=power(x,n>>1);
        result=result*temp*temp;
        return result;
    }
};