Medium data structure and algorithm practice puzzle.
Given n, return true if it's prime, meaning it's bigger than 1 and only divisible by 1 and itself. Try dividing by every number from 2 up to the square root of n. You can stop there, because any bigger factor pairs with a smaller one you already checked. Prime numbers are what RSA encryption is built on.
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 Reading Integrity Check, a pipeline you can run and download. See every Software Engineer project.
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