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.)

Similar: 152. Maximum Product Subarray

42. Trapping Rain Water

 

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