Easy data structure and algorithm practice puzzle.
Given a stream of timestamps and a cap, return the ones you keep, oldest first. Network updates can arrive late or twice, so skip any stamp that isn't newer than the newest one you already kept. If keeping one puts you over the cap, drop the oldest. That's a ring buffer: a short, fixed-size history that never grows.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Ticket Replay Log, a pipeline you can run and download. See every Software Engineer project.
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