class Solution {
public:
    double quick(double base, int exponent){
        double res = 1;
        while(exponent){
            if(exponent & 1)   res *= base;
            base *= base;
            exponent >>= 1;   

        }
        return res;
    }
    double Power(double base, int exponent) {
        bool flag = false;
        if(exponent < 0)    flag = true, exponent = -exponent;
        double res = quick(base, exponent);
        if(flag)    res = 1 / res;
        return res;
    }
};