I can solve all that programming questions with no problem but: the first question is the kind of interview question that irks me (although i know how to solve it using XOR). But,I would rather have a spare variable IF IT WILL MAKE MY CODE MORE READABLE. It's not all about saving a variable and memory space. The other questions are just specifics on the programming language. You can learn those things in a day. But algorithms and data structures is the meat and potatoes of everything and those are things that are innate to any 'good' programmers.