Hard data structure and algorithm practice puzzle.
Given an array and a target, return the sum of the three numbers that comes closest to the target. Sort it, fix one number, and use two pointers on the rest, moving toward the target. Keep the sum with the smallest distance from the target. If you hit it exactly, return right away. You return the SUM, not the numbers.
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 Ledger Balancer, a pipeline you can run and download. See every Software Engineer project.
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