class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        vector<int> res=nums;
        if(nums.empty())
            return res;

        for(int i=0; i<nums.size(); i++)
            nums[i] = i==0? nums[i]:nums[i-1]*nums[i];
        for(int i=nums.size()-1; i>=0; i--)
            res[i] = i==res.size()-1? res[i]:res[i]*res[i+1];
        for(int i=0; i<res.size(); i++){
            if(i==0)
                res[i] = 1*res[i+1];
            else if(i==res.size()-1)
                res[i] = nums[i-1]*1;
            else
                res[i] = nums[i-1]*res[i+1];
        }
        return res;
    }
};