class Solution {

public:

    vector<int> productExceptSelf(vector<int>& nums) {

        int size = nums.size();

        vector<int> ret(size, );

        long long product = ;

        int countZero = ;

        int ind = -;   // 0-index

        for(int i = ; i < size; i ++)

        {

            if(nums[i] == )

            {

                countZero ++;

                ind = i;

            }

        }

        //special case for 0

        if(countZero == )

        {//no zero

            for(int i = ; i < size; i ++)

                product *= nums[i];

            for(int i = ; i < size; i ++)

                ret[i] = mydivide(product, nums[i]);

        }

        else if(countZero == )

        {//1 zero

            for(int i = ; i < size; i ++)

            {

                if(i != ind)

                    product *= nums[i];

            }

            ret[ind] = product; //others are 0s

        }

        else

        {//2 or more zeros

            ;   //all 0s

        }

        return ret;

    }

    int mydivide(long long product, int divisor)

    {// guaranteed that divisor is not 0

        int sign = ;

        if((product < ) ^ (divisor < ))

            sign = -;

        if(product < )

            product = -product;

        if(divisor < )

            divisor = -divisor;

        //to here, product and divisor are positive

        int ret = ;

        while(true)

        {

            int part = ;   //part quotient

            int num = divisor;

            while(product > num)

            {

                num <<= ;

                part <<= ;

            }

            if(product == num)

            {

                ret += part;

                return sign * ret;

            }

            else

            {

                num >>= ;

                part >>= ;

                ret += part;

                product -= num;

            }

        }

    }

};