Not Sure if you still need an answer but the problem is that you are declaring your list in the class and never clear it, so on the first test i assume that your programm works but on the second one he is just adding things to the list of the last test and that is what gets you this weird solutions. try it again and write as first line in the singlePermutations method: "list.clear();" so the list is empty when you start a new test. Hope i could help :)