CC35:加法运算替代

class AddSubstitution {
public:
    int calc(int a, int b, int type) {
        // write code here
        int result=0;
        switch(type){
            case 1:
                for(int i=0;i<b;i++)
                    result+=a;
                break;
            case 0:
                if (b == 0) return -1;
	            if (a < b) return 0;
                while (a >= b)
                    {
                        int temp = 1;
                        while (b*temp < a)
                        {
                            temp = temp << 1;
                        }
                        if (b*temp == a)
                        {
                            result += temp;
                            a = 0;
                        }
                        else
                        {
                            result += (temp >> 1);
                            a = a - b*(temp >> 1);
                        }
                    }
                break;
            case -1:
                b=-b;
                result=a+b;
                break;
            default:
                break;
        }
        return result;
    }
};