Traversing directories without using recursion?

Question

The Problem I need to write a simple software that, giving certain constraints, appends to a list a series of files. The user could choose between

Answer 1

Right now I'm doing the stupidest thing ...

Recursion is neither "stupid" or necessarily inefficient. Indeed in this particular case, a recursive solution is likely to be more efficient than a non-recursive one. And of course, the recursive solution is easier to code and to understand than the alternatives.

The only potential problem with recursion is that you could overflow the stack if the directory tree is pathologically deep.

If you really want to avoid recursion, then the natural way to do it is to use a "stack of list of File" data structure. Each place where you would have recursed, you push the list containing the current directory's (remaining) File objects onto the stack, read the new directory and start working on them. Then when you are finished, pop the stack and continue with the parent directory. This will give you a depth-first traversal. If you want a breadth-first traversal, use a "queue of File" data structure instead of a stack.