Balanced binary tree (AVL)~

Balanced binary tree is actually an upgraded version of binary sort tree , It improves the efficiency of query

• Balance factor ： The difference between the height of the left subtree minus the height of the right subtree , There are positive, negative and zero
• Balanced binary trees ： The absolute value of the balance factor of each node is not greater than 1

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a key ： The adjustment of balanced binary tree

• LR, Intermediate nodes L, Root node R
• RL, Intermediate nodes R, Root node L
• LL, Root node R
• RR, Root node L

eg： Sequence by keyword {16,3,7,11,9,26,18,14,15} Build a tree AVL Trees （ Balanced binary trees ), After the construction is completed, delete the nodes in turn 16、15、11. Give the detailed operation process , Mark the balance factor above the node in the title , Use the dotted line to frame the 3 Nodes .

answer ：

Before deleting

After deleting