Medium data structure and algorithm practice puzzle.
Given when each entry was built, when it was last used, and how many can be kept, return the positions to evict, lowest first. Keep the most recently USED entries and ignore when they were built. If two were last used at the same time, evict the lower position first. Pick the wrong timestamp and the entry everyone runs every day is the first one you throw away.
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 Reading Calendar Merger, a pipeline you can run and download. See every Software Engineer project.
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