Medium data structure and algorithm practice puzzle.
A gateway allows at most max calls in any window of window seconds. Given sorted request times, return how many calls get rejected. A call is allowed if fewer than max ALLOWED calls happened in the last window seconds. Calls that happened exactly window seconds ago no longer count. A rejected call doesn't count against the limit, which is the rule people usually get wrong.
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 Request Smoothing Rig, a pipeline you can run and download. See every Software Engineer project.
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