Medium data structure and algorithm practice puzzle.
Crates sit in a row on a beam. Given their weights, return the position where everything to the left weighs the same as everything to the right, not counting the crate at that position. Return the leftmost one, or -1 if there isn't one. Weights can be negative.
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 Request Parser, a pipeline you can run and download. See every Software Engineer project.
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