Easy data structure and algorithm practice puzzle.
Given an array and k, return the k largest values, biggest first. Sort from biggest to smallest and take the first k. That's O(n log n). Follow-up: a heap that only ever holds k items does it in O(n log k), which really matters when n is huge and k is small.
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 Match Calibrator, a pipeline you can run and download. See every Software Engineer project.
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