Easy data structure and algorithm practice puzzle.
A stutter is a run of slow frames, and players feel it even when the average frame rate looks fine. Given a list of frame times in milliseconds and a window size k, return the index where the worst run of k frames in a row starts, meaning the run with the largest total. Ties go to the earlier run, and fewer than k frames means -1. Use a sliding window: sum the first k frames, then move one frame at a time, adding the frame coming in and subtracting the one going out.
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 Entity Window Auditor, a pipeline you can run and download. See every Software Engineer project.
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