Medium data structure and algorithm practice puzzle.
Given two vectors a and b, return their cosine similarity, rounded to 3 decimals. Take the dot product, then divide by the length of a times the length of b. The answer runs from -1 to 1, where 1 means they point the same way. Dividing by length ignores size, so a long and a short document on the same topic still score close to 1.
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 Smoothing Rig, a pipeline you can run and download. See every Software Engineer project.
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