Medium data structure and algorithm practice puzzle.
Given two arrays that line up, hours and rates, return the total fee. Multiply each hour count by the rate at the same position, and add them all up. That's called a dot product, and it's the same math at the heart of matrix multiplication and every neural network layer.
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 Clause Streak Finder, a pipeline you can run and download. See every Software Engineer project.
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