Merge two sorted arrays with O(1) extra space

Merge two sorted arrays with O(1) extra space is a DSA topic. In plain words you use it for names A→Z in the roll list. Don’t start with a slogan — start with that picture.

Smallest example: n log n vs n². Type it, run it, and say what you see. If you can do that from memory, you know Merge two sorted arrays with O(1) extra space.

From the example next to this theory — Merge two sorted arrays with O(1) extra space: dry-run [4, 1, 3].

Trap — unstable sort when equal keys matter. Fix that before you talk about advanced DSA.

Viva — what is Merge two sorted arrays with O(1) extra space? Then show n log n vs n². Then name the trap.