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I have a question regarding the insertion in an AVL Tree. I noticed that there are some cases in which for example, after you inserted an element, both the parent and it's child are breaking the AVL condition. For example here https://www.youtube.com/watch?v=EsgAUiXbOBo, at min. 12:50, when after 1 was inserted, both 4 and 3 are breaking the AVL condition. My question is on which node should we do the rotation. The closest one to the root (in this case is the root itself) or the one who is farthest from the root, as we would get two different trees in those cases? Or is it correct either way?

Jabberwocky
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gliga bogdan
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1 Answers1

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Rotation starts from the bottom (the inserted node).

Let's consider having balanced all nodes up to P (included). So the subtree of P is perfectly balanced. We go to P's parent (Q). The subtree of Q is checked and (eventually) rotated. The result tree (the root may have changed if a rotation was performed) is perfectly balanced. Advance up again.

Hristo Venev
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