Hard data structure and algorithm practice puzzle.
Given a search space of size n and a number of Grover iterations k, return the chance of finding the marked item, rounded to 4 decimals. Let theta = arcsin(1 / sqrt(n)). The answer is sin((2k + 1) x theta) squared. Too few iterations and you haven't turned far enough. Too many and you overshoot.
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 Shot Change Feed, a pipeline you can run and download. See every Software Engineer project.
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