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

Example:

Input:  [1,2,3,4]
Output: [24,12,8,6]

Constraint: It's guaranteed that the product of the elements of any prefix or suffix of the array (including the whole array) fits in a 32 bit integer.

Note: Please solve it without division and in O(n).

Follow up:
Could you solve it with constant space complexity? (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) {
        int n = nums.size();
        vector<int> res(n,1);
        
        for(int i=0;i<n;i++){
            if(i>=1) res[i]=res[i-1]*nums[i-1];
        }
        //右侧
        int right = 1;
        for(int j=n-1;j>=0;j--){
            res[j]*=right;
            if(j>0) right*=nums[j];
        }
        return res;
    }
};