Medium data structure and algorithm practice puzzle.
Given a pile of stone weights, keep smashing the two heaviest together. If they weigh the same, both are destroyed. If not, the difference goes back in the pile. When one stone or none is left, return its weight, or 0. Sort the pile each round to find the two heaviest. A max-heap does that faster.
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 Parser, a pipeline you can run and download. See every Software Engineer project.
Browse all 576 puzzles