Medium data structure and algorithm practice puzzle.
Given a scale as pitch classes (0 to 11) and a MIDI note, return true if the note is in the scale. Take the note mod 12 first. That turns every octave of the same note into one number, so 60 and 72 both become 0. Then just check whether the scale includes it.
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 Track Smoothing Rig, a pipeline you can run and download. See every Software Engineer project.
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