Medium data structure and algorithm practice puzzle.
Given an array of numbers, sort it with bubble sort. Walk through and swap any two neighbors that are out of order. After each pass, the biggest value left has bubbled to the end, so the next pass can stop one spot sooner. It's O(n squared) and nobody ships it, but it's worth writing once so the faster sorts have something to beat.
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 Login Quantile Rig, a pipeline you can run and download. See every Software Engineer project.
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