Medium data structure and algorithm practice puzzle.
Given sorted request times, a window length, and a limit, return how many requests are allowed. A request is allowed if fewer than limit ALLOWED requests happened in the window before it. Requests exactly windowMs ago no longer count. Rejected requests don't use up the limit. This site's sign-in route is protected by this exact kind of limiter.
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.
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