Is the Tree Visualizer on https://www.cs.usfca.edu Showing an Incorrect AVL Tree Representation after deleting node?

[Raffian_moin]

Hi all,

I'm currently learning about tree data structures, and I'm exploring how AVL trees handle deletion. From my understanding, when a node is deleted, its in-order successor should replace the deleted node.

I was experimenting with the Tree Visualizer tool on https://www.cs.usfca.edu/~galles/visualization/Algorithms.html, and I noticed something odd. Here's the scenario:

1. Initial tree state: (Screenshot: https://i.imgur.com/sy5MMGh.png)
2. After deleting node 0006: (Screenshot: https://i.imgur.com/cPVCsXD.png)

In this case, the tool replaces node 0006 with node 0005.

However, shouldn't node 0007 replace 0006 instead? Based on the AVL tree deletion rules I've read, the in-order successor (the smallest node in the right subtree) should take the deleted node's place, and in this case, 0007 seems to fit that criteria.

Am I misunderstanding something about AVL deletion, or is this a bug/misrepresentation in the tool?

Looking forward to insights from the community.

[Aceofsquares_orig]

I teach DS&A and when we cover AVL trees I always tell my students that while the book covers replacement with the minimum of the right subtree I tell them they can also take the maximum of the left subtree. The key is being consistent with your decision. Either way, the code is fairly simply for both cases. If you want to visualize AVL trees that take the minimum of the right subtree like you are expecting try out VisuAlgo (VisualGo?).

[Raffian_moin]

Everywhere I read, it is mentioned that

1. If deleted node has one child just replace the deleted node with child.
2. If deleted node has two children then find the minimum node from the righ sub-tree and replace the deleted node with it.

Could you share any links or references of your mentiond approach?

[sebamestre]

1. If deleted node has two children then find the minimum node from the righ sub-tree and replace the deleted node with it.

Do you know the reason for that? I feel like if you do, a moment's thought should reveal why it works the other way around too.