Depends. If there is a minimum value, every value will appear, and you don't want dups, then this is doable. Say the streams are of natural numbers starting w

Depends. If there is a minimum value, every value will appear, and you don't want dups, then this is doable. Say the streams are of natural numbers starting with 1, and every natural number will appear within each stream. The obvious thing to do is to not even bother doing anything with the streams except to drain them, and just write the natural numbers in order to stdout! Yes, I'm chuckling. It's a trivial toy problem. It's not a useful problem to solve. But the question may be there just to get you to think of just this, and to ask questions.