The problem with the BFS/DFS questions is that you're playing a forced game of knifey spoony: They expect you to write it in the recursive fashion and then try

The problem with the BFS/DFS questions is that you're playing a forced game of knifey spoony: They expect you to write it in the recursive fashion and then try to stump you with "oh but how does that do on large structures?!" .. Stackoverflow. Then they'll try to force you to do tail recursion.