```
class Solution {
public:
vector<int> productExceptSelf(vector<int>& nums) {
int n = nums.size();
vector<int> res(n, 0);
res[0] = 1;
// first pass, each element contains product up to and
// not including the current element in nums
for(int i = 1; i < n; i++) {
res[i] = res[i-1] * nums[i-1];
}
int product = 1;
for(int i = n-1; i >= 0; i--) {
res[i] = res[i] * product;
product = product * nums[i];
}
return res;
}
};
```