Hard data structure and algorithm practice puzzle.
Given a list of points and a list of centroids, return the index of the closest centroid for each point. For each point, check every centroid and keep the one with the smallest squared distance. You can skip the square root, since it never changes which one is closest. This is the assign step of k-means.
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 Throughput Report, a pipeline you can run and download. See every Software Engineer project.
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