AVL Trees
These aren't used much in practice.
The AVL tree is another structure supporting O(log n) search, insertion, and removal.
It is more rigidly balanced than red–black trees, leading to slower insertion and removal but faster retrieval.
This makes itattractive for data structures that may be built once and loaded without reconstruction, such as language dictionaries (or program dictionaries, such as the opcodes of an assembler or interpreter)