Easy data structure and algorithm practice puzzle.
Given a sorted list of snapshot times and a target time, return the index of the last snapshot at or before the target. If the target is earlier than every snapshot, return -1. That snapshot and the one after it are the two moments the target falls between, which is what you need to draw a player smoothly between network updates.
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 Event Quantile Rig, a pipeline you can run and download. See every Software Engineer project.
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