Hard data structure and algorithm practice puzzle.
Given a page table as a tree and an address as one index per level (0 means left, 1 means right), return the physical frame number, or -1 for a page fault. A node holds a frame number if it's mapped and 0 if it isn't. You have to make it all the way down. Hitting a missing node, or ending on a 0, is a fault. Every memory access your program makes does this walk.
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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