Medium data structure and algorithm practice puzzle.
In a scene graph every object is placed relative to its parent: a sword relative to a hand, the hand relative to an arm, the arm relative to the knight. Given parent[i] (-1 for no parent) and each object's local x offset, return every object's world x: its own offset plus its parent's world x. Parents aren't guaranteed to come first in the list, so work each one out recursively up the chain, and use memoization so no object is worked out twice.
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 Entity Hierarchy Report, a pipeline you can run and download. See every Software Engineer project.
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