The First Repeat, Turbo Mode

In the Searching unit you found the first repeated card with a list and a nested loop. The turbo version uses a set — same answer, way less work. 🎴⚡

You get a list of cards. Print the first card that appears a second time, or no repeats.

Example:

Input: cards = ["sun", "moon", "star", "moon", "sun"] Output: moon

"sun", "moon", and "star" are all new the first time. The second "moon" is the first card seen a second time.