Sure! In steamroll, if you didn't have the test cases, you'd have no idea how far deep the arrays go. Maybe 2, Maybe 12. Like in factorial, you may only be doing ^6 or ^106. When writing the code, you don't know how deep you will need to go. Factorial you could for loop, but in steamroll not so much as in factorial you know from the onset how many. But in steamroll, until the code fully dissects the array, you'd never know how many dimensions the array has.