Medium data structure and algorithm practice puzzle.
Given two IPv4 addresses as four numbers each and a prefix length, return true if they're on the same subnet, meaning their first prefix-length bits match. Compare byte by byte, masking each one, and stop once you've used up the prefix. Routers ask this about every packet: same subnet means deliver it directly.
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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