Medium data structure and algorithm practice puzzle.
Given n, return how many positive whole numbers divide it evenly. So 6 has 4: 1, 2, 3, and 6. Try every number from 1 to n and count the ones that leave no remainder. Follow-up: divisors come in pairs, so checking up to the square root of n is enough if you count each pair once.
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 Range Service, a pipeline you can run and download. See every Software Engineer project.
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