【剑指offer】数值的整数次方

double Power(double base, int exponent) {
        if(exponent < 0) //处理负数，这里最开始没想到 卡了很久
        {
            base = 1 / base;
            exponent = (-exponent);
        }
        double d = base;
        double ans = 1;
        int bit = 1;
         
        while(exponent != 0)
        {
            if((exponent & bit) != 0) //如果exponent的当前位是1
            {
                ans *= d;
                exponent &= (exponent - 1);
            }
            d = d * d;
            bit = bit << 1;
        }
 
        return ans;
    }

double Power(double base, int exponent) {
        if(exponent < 0)
        {
            base = 1 / base;
            exponent = (-exponent);
        }
        if(exponent == 0)
            return 1;
        else
        {
            double tmp = Power(base, exponent >> 1);
            if((exponent & 0x1) == 0)
                return tmp * tmp;
            else
                return tmp * tmp * base;
        }
    }