Medium data structure and algorithm practice puzzle.
Given a binary tree, return the number of levels from the root down to the CLOSEST leaf. An empty tree is 0. If a node has only one child, you have to go down that side, because a missing child isn't a leaf. Otherwise, it's 1 plus the smaller of the two sides. That one-child case is the whole puzzle.
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 Typeahead, a pipeline you can run and download. See every Software Engineer project.
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