Leetcode 238 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.).

Solution 1: Itrate from left to right, update the value res[i] to be product of all nums on the left. then iterate from right to left, res to multiply the product of nums of right.

 public class Solution {  
   public int[] productExceptSelf(int[] nums) {  
     int n=nums.length;  
     int[] res=new int[n];  
     res[0]=1;  
     for (int i=1; i<n; i++) {  
       res[i]=nums[i-1]*res[i-1];  
     }  
     int right=1;  
     for (int i=n-1; i>=0; i--) {  
       res[i]*=right;  
       right*=nums[i];  
     }  
     return res;  
   }  
 }