Easy data structure and algorithm practice puzzle.
Given predictions and true labels, return the fraction the model got right, rounded to 3 decimals. Walk both lists together and count the matches, then divide by the length. Watch out: if 99 out of 100 emails are clean, a spam filter that never flags anything still scores 0.99. That's why lopsided data needs precision and recall.
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 Archive Tier, a pipeline you can run and download. See every Software Engineer project.
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