Easy data structure and algorithm practice puzzle.
Given a binary tree, return the root's value, or null if the tree is empty. There's nothing to walk. The root is the first node. Returning null for an empty tree, instead of 0, keeps it separate from a root that actually holds 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 Shot Search Index, a pipeline you can run and download. See every Software Engineer project.
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