An AVL tree is a balanced binary search tree where the height of the two child subtrees differ by at most one. Look-up, insertion and deletion are all O(log(n)) in both the average and worst cases. Additions and deletions may require the tree to be rebalanced by one or more tree rotations. The AVL tree is named for its inventors, Adelson-Velskii and Landis (1962).
See also: Red-Black tree