Medium data structure and algorithm practice puzzle.
Given a network as an adjacency list, return how many separate pieces it's split into. One means everything can reach everything. Loop over every router, and each time you find one you haven't visited, count a new piece and visit everything connected to it. That outer loop is the part people forget.
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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