AVL TreesIn computer science, an AVL tree is the first-invented self-balancing binary search tree. In an AVL tree the heights of the two child subtrees of any node differ by at most one, therefore it is also known as height-balanced. Lookup, 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 after its two inventors, G.M. Adelson-Velsky and E.M. Landis, who published it in their 1962 paper "An algorithm for the organization of information."
The balance factor of a node is the height of its right subtree minus the height of its left subtree. A node with balance factor 1, 0, or -1 is considered balanced. A node with any other balance factor is considered unbalanced and requires rebalancing the tree. The balance factor is either stored directly at each node or computed from the heights of the subtrees.
