void checkWord(char *currentWord, List *possible_letters, List *valid_permutations)
{
	ListIterator *iter = list_get_iterator(possible_letters);

	// Leaf in the recursion tree
	if (list_size(possible_letter == 0))
	{
		if(Dictionary::isValid(currentWord))
                     list_prepend(valid_permutations, currentWord);
	}

	for (iter = list_first(possible_letters); iter != list_end(possible_letters);
             iter = list_iterator_next(iter))
        {
	    // stringAddLetter also allocates memory :)
	    char *word = stringAddLetter(currentWord, *(char *)list_iterator_get_value(iter));
	    checkWord(word, list_remove_item_at_iterator(possible_letter, iter), valid_permutations);
	}

	if (currentWord)
		free(currentWord);
}

List* generateValidPermutations(const char *word)
{
	List *valid_permutations = list_new();
        int n = strlen(word), i = 0;
	List *possible_letters = list_new();

	for (i = 0; i < n; i ++)
		list_append(possible_letters, word[i]);

	checkWord(NULL, possible_letters, valid_permutations);

	return valid_permutations;
}