A Product Array Puzzle

Given an array arr[] of n integers, construct a Product Array prod[] (of same size) such that prod[i] is equal to the product of all the elements of arr[] except arr[i]. Solve it without division operator and in O(n).

 

Example:
arr[] = {10, 3, 5, 6, 2}
prod[] = {180, 600, 360, 300, 900}

 

    public static int[] selfExcluding(int[] input){
        if(input == null || input.length == 0) return null;
        int len = input.length;
        int[] output = new int[len];
        for(int i = 0; i < len; i ++){
            output[i] = 1;
        }
        int left = 1, right = 1;
        for(int i = 1; i < input.length; i ++){
            left *= input[i - 1];
            output[i] *= left; 
            right *= input[len - i];
            output[len - i - 1] *= right;
        }
        return output;
    }