Create an  AVL Tree for the given values 21, 26, 30, 9, 4, 14, 28, 18,15,10, 2, 3, 7.  What are the leaf nodes elements of the AVL tree.

To create an AVL Tree for the given values 21, 26, 30, 9, 4, 14, 28, 18, 15, 10, 2, 3, 7, we will follow these steps:

1. Start with an empty AVL Tree.
2. Insert the first value, 21, as the root of the tree.
3. Insert the next value, 26, as the right child of the root.
4. Insert the next value, 30, as the right child of 26.
5. Insert the next value, 9, as the left child of 21.
6. Insert the next value, 4, as the left child of 9.
7. Insert the next value, 14, as the right child of 4.
8. Insert the next value, 28, as the left child of 30.
9. Insert the next value, 18, as the right child of 14.
10. Insert the next value, 15, as the left child of 18.
11. Insert the next value, 10, as the left child of 15.
12. Insert the next value, 2, as the left child of 4.
13. Insert the next value, 3, as the right child of 2.
14. Insert the last value, 7, as the right child of 9.

The resulting AVL Tree will look like this:

    21
   /  \
  9    26
 / \     \
4   14    30

/ \ \ / 2 7 18 28
3

The leaf nodes of the AVL Tree are the nodes that do not have any children. In this case, the leaf nodes are: 3, 7, 18, and 28.