Medium data structure and algorithm practice puzzle.
Given the pages a program uses, in order, and how many frames of memory it has, return how many page faults happen under least recently used (LRU) replacement. On a hit, that page becomes the most recent. On a miss, count a fault, and if memory is full, kick out the least recently USED page, not the oldest one loaded.
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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