That is a perfect example for why you need CS in engineering! Please do a right click view source on this page, what do you see? Look at the comment structure on this page, what do you see? Nobody could work with any of those without using recursive depth first traversal. And once someone understands recursion, the implementation of it is absolutely trivial and obvious. Why would you not use that? The same goes for all the other CS textbook problems, they are specialized screwdrivers that are useless until they aren't.