Tree-avl Tree

AVL Tree
The balance tree is most concerned with the prevention of tree imbalance, if a new element crisis to the tree balance, you can immediately correct. You can have a local refactoring tree (AVL method) or rebuild the entire tree (DSW) method.
The AVL tree is a self balanced binary lookup tree in which the maximum difference in height of two subtrees of any node in the AVL tree is one, so it is also known as a highly balanced tree. Additions and deletions may require one or more tree rotations to rebalance the tree.
Balance Factor BF (): Height of the right subtree-Zuozi height
The balance factor of AVL can be 0,1,-1
If a new node is inserted into a balanced binary search tree, it creates an imbalance. At this point, you must adjust the structure of the tree to make it balanced.
Insert operation: Inserts a new node, the associated node state in the AVL tree changes. Therefore, after inserting the new node, you need to backtrack from the insertion position along the Shangen path to check the balance factor of each node.
Delete operation: Set Q is the parent node of the deleted node
If the deletion occurs in the left subtree of Q, then the BF (q) minus 1
If the deletion occurs in the right subtree of Q, then the BF (q) plus 1