The document discusses 2-3 trees, which are trees where each internal node has either 2 or 3 children and all leaves are at the same depth. Items are inserted by adding them to leaves, which may cause leaves to split into two. Items are deleted by removing them from leaves, which may cause leaves to merge. This allows 2-3 trees to maintain balance more easily than binary search trees during insertions and deletions.

1. 2-3 Trees Lecture 16

5. A 2-3 Tree of height 3

17. Consider the two trees contain the same data items. 30 90 10 50 20 40 80 70 100 60 A balanced binary search tree 50 30 40 60 80 100 70 90 10 20 A 2-3 tree

19. 60 30 90 30 50 80 100 40 20 39 38 37 70 36 35 34 1) The binary search tree after a sequence of insertions

20. 37 34 50 30 35 60 39 38 40 80 100 36 10 20 70 90 2) The 2-3 tree after the same insertions.