Product of Array Except Self

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Solve it without division and in O(n).

For example, given [1,2,3,4], return [24,12,8,6].

Follow up:
Could you solve it with constant space complexity? (Note: The output array does not count as extra space for the purpose of space complexity analysis.)

class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        vector<int> res(nums.size(),);

        int i;
        for(i=;i<nums.size();i++)
        {
            res[i]=res[i-]*nums[i-];
        }
        int right=;
        for(i=nums.size()-;i>=;i--)
        {
            res[i]*=right;
            right*=nums[i];
        }
        return res;
    }
};