Easy data structure and algorithm practice puzzle.
Given n, return true if it's a perfect number, meaning it equals the sum of its divisors other than itself. So 6 is perfect, because 1 + 2 + 3 = 6. Check divisors up to the square root of n, and each one you find gives you its partner n / d for free. Don't count the square root twice, and don't count n itself.
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 Stats Roll-up, a pipeline you can run and download. See every Software Engineer project.
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