Hard data structure and algorithm practice puzzle.
Given a binary tree and a target, return true if some path from the root down to a LEAF adds up to exactly the target. Subtract each node's value from the target on the way down. Only check for 0 when you reach a leaf. Values can be negative, so you can't give up early just because the remainder went below 0.
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 Trip Ordered Index, a pipeline you can run and download. See every Software Engineer project.
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