Solution - flatten

gistfile1.txt

public Integer[] myFlatten(Object[] input) throws IllegalArgumentException {

        if (input == null) return null;

        List<Integer> result = new ArrayList<Integer>();

        for (Object e : input) {
            if (e instanceof Integer) {
                result.add((Integer) e);
            } else if (e instanceof Object[]) {
                result.addAll(Arrays.asList(flatten((Object[]) e)));
            } else {
                throw new IllegalArgumentException("Wrong Input");
            }
        }
        return result.toArray(new Integer[result.size()]);
    }