class Solution {public:    double pow(double x, int n) {        if(n < 0) return 1.0/power(x, -n);        return power(x, n);    }        double power(double x, int n){        if(n == 0) return 1.0;        double half = power(x, n/2);        if(n%2 == 0) return half*half;        return half*half*x;    }};