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.)

public class Solution {
    public int[] productExceptSelf(int[] nums) {
        int[] res = new int[nums.length];
        res[0] = 1;

        for(int i=1;i<nums.length; i++){
            res[i] = res[i-1] * nums[i-1];
        }
        int r = 1;
        for(int i= nums.length-1; i>=0;i--){
            res[i] *= r;
            r *= nums[i];
        }
        return res;
    }
}