Hard data structure and algorithm practice puzzle.
Given an array, return the length of the shortest stretch that, if you sorted just that stretch, would make the whole array sorted. Find the first spot from the left where it stops rising, and the first from the right where it stops falling. Take the min and max between them, then widen the stretch until everything outside it fits. Already sorted is 0.
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 Frame Burst Detector, a pipeline you can run and download. See every Software Engineer project.
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