Have We Met?

The party host never forgets a face — because the host keeps a set. 🎉

You get the guests who came before and one name at the door. Print welcome back if they've visited, or new face if not. Remember Unit 0's search loop? A set does that check in ONE step: name in guestset.

Example:

Input: guests = ["mia", "leo", "zara"], name = "leo" Output: welcome back

"leo" is inside the guest set, so it's a familiar face — print welcome back.

Input: guests = ["mia", "leo"], name = "finn" Output: new face

"finn" isn't in the set at all, so print new face.