Easy data structure and algorithm practice puzzle.
Given a class index and the number of classes, return an array of zeros with a single 1 at that index. So class 2 out of 4 is [0, 0, 1, 0]. Feeding the raw number to a model would suggest class 3 is "bigger" than class 1. One-hot encoding avoids giving the categories a fake order.
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 Sample Streak Finder, a pipeline you can run and download. See every Software Engineer project.
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