数值的整数次方

class Solution {
public:
    double Power(double base, int exponent) {
        if(base==0) return 0;
        if(exponent==0) return 1;
        double product=1;
        if(exponent<0) base=1/base;
        while(exponent)
        {
            product *= base;
            if(exponent>0) exponent--;
            else exponent++;
        }
        return product;
    }
};