AVL TREE insert， delete，rotation，algorithm

#include <cstdio>

class AVLNode{
public:
	AVLNode(int key){
		this->key = key;
		left = NULL;
		right = NULL;
		balance = 0;
	}

	AVLNode *left, *right;
	int key;
	/*
	 The record key stored on the tree nodes, can be of any comparable type, we use int for simplicity.
	 Usually the actual record data is also strored on the tree nodes, but we skip it for simplicity, too.
	*/
	int balance; 
	/*
	 balance=(height of right subtree)-(height of left subtree)
	 balance=0: entirely balanced
	 balance=1: right heavy, but still balanced
	 balance=-1: left heavy, but still balanced
	 |balance|>1: unbalanced
	*/
};

class AVLTree  
{
public:
	AVLTree() {this->root = NULL;}
	~AVLTree() {destroy(root);}
	AVLNode* insert(int key);
	void printTree();
	int getHeight() {return rGetHeight(root);};
	AVLNode* remove(int key);
	//This method removes the node with the given key from the tree
	//If such node does not exist, NULL will be returned
	//Otherwise, a pointer to the removed node is returned
	//You may use existing member functions or define other member functions to complete the task
private:
	AVLNode *root;
	AVLNode *tmp;     //using to point to subroot in findMin function
	AVLNode *temp;    //using to point to subroot in rRemove function
	AVLNode *rInsert(int key, AVLNode* &subRoot, bool &heightChanged);
	AVLNode *rRemove(int key, AVLNode* &subroot, bool &heightChanged); //Remove the particular node with key
	AVLNode *findMin(AVLNode * &subroot, bool &heightChanged);  //Find the leftest node of right subtree 
	void balance1(AVLNode* &subRoot);//Re-balance for case 1 violation
	void balance2(AVLNode* &subRoot);//Re-balance for case 2 violation
	void balance3(AVLNode* &subRoot);//Re-balance for case 3 violation
	void balance4(AVLNode* &subRoot);//Re-balance for case 4 violation
	void balance5(AVLNode* &subRoot);//Re-balance for case 5 violation:left-left-balance
	void balance6(AVLNode* &subRoot);//Re-balance for case 6 violation:right-right-balance
	void destroy(AVLNode *subRoot);	
	int rGetHeight(AVLNode *subRoot);
};


//The Queue data structure is used to help print the tree
class QueueNode
{
public:
	QueueNode(AVLNode *data, bool isLeading=false) {this->data = data; this->isLeading=isLeading;  next=NULL;}
	AVLNode *data;
	//data is NULL if the node corresponds to a hole in the tree
	bool isLeading;
	//If the current node is the leading node in a level
	QueueNode *next;
};

class Queue
{
public:
	Queue() {front = NULL; rear = NULL;}
	~Queue();
	void enqueue(AVLNode *data, bool isLeading=false);
	QueueNode* dequeue();
	bool isEmpty() {return !front;}
private:
	QueueNode *front, *rear;
};