Low-Level Design Exercises

Take money, dispense a product, give change — and behave correctly at every step in between.

Write log events to several destinations, filtered by level, without the caller knowing where they go.

Send the right car to each call, serve stops in a sensible order, and never move with the doors open.

Lend physical copies, take them back, and queue members fairly for books that are all out.

Record shared expenses split several ways, keep every balance exact, and suggest how to settle up.

Enforce the full rules of chess for two players, including the moves that break the usual patterns, with undo.

Find rooms free for a range of nights, book them without double-booking, and follow each stay from booking to checkout.