public class AVLNode {public int data;//保存节点数据public int depth;//保存节点深度public int balance;//是否平衡public AVLNode parent;//指向父节点public AVLNode left;//指向左子树public AVLNode right;//指向右子树
​public AVLNode(int data){this.data = data;depth = 1;balance = 0;left = null;right = null;}}

public void insert(AVLNode root, int data){//如果说插入的数据小于根节点，往左边递归插入if (data < root.data){if (root.left != null){insert(root.left, data);}else {root.left = new AVLNode(data);root.left.parent = root;}}//如果说插入的数据小于根节点，往左边递归插入else {if (root.right != null){insert(root.right, data);}else {root.right = new AVLNode(data);root.right.parent = root;}}//插入之后，计算平衡银子root.balance = calcBalance(root);// 左子树高，应该右旋if (root.balance >= 2){// 右孙高，先左旋if (root.left.balance == -1){left_rotate(root.left);}right_rotate(root);}// 右子树高，左旋if (root.balance <= -2){// 左孙高，先右旋if (root.right.balance == 1){right_rotate(root.right);}left_rotate(root);}//调整之后，重新计算平衡因子和树的深度root.balance = calcBalance(root);root.depth = calcDepth(root);
}

    // 右旋private void right_rotate(AVLNode p){// 一次旋转涉及到的结点包括祖父，父亲，右儿子AVLNode pParent = p.parent;AVLNode pLeftSon = p.left;AVLNode pRightGrandSon = pLeftSon.right;// 左子变父pLeftSon.parent = pParent;if (pParent != null){if (p == pParent.left){pParent.left = pLeftSon;}else if (p == pParent.right){pParent.right = pLeftSon;}}pLeftSon.right = p;p.parent = pLeftSon;// 右孙变左孙p.left = pRightGrandSon;if (pRightGrandSon != null){pRightGrandSon.parent = p;}p.depth = calcDepth(p);p.balance = calcBalance(p);pLeftSon.depth = calcDepth(pLeftSon);pLeftSon.balance = calcBalance(pLeftSon);}

    private void left_rotate(AVLNode p){// 一次选择涉及到的结点包括祖父，父亲，左儿子AVLNode pParent = p.parent;AVLNode pRightSon = p.right;AVLNode pLeftGrandSon = pRightSon.left;// 右子变父pRightSon.parent = pParent;if (pParent != null){if (p == pParent.right){pParent.right = pRightSon;}else if (p == pParent.left){pParent.left = pRightSon;}}pRightSon.left = p;p.parent = pRightSon;// 左孙变右孙p.right = pLeftGrandSon;if (pLeftGrandSon != null){pLeftGrandSon.parent = p;}p.depth = calcDepth(p);p.balance = calcBalance(p);pRightSon.depth = calcDepth(pRightSon);pRightSon.balance = calcBalance(pRightSon);}

    public int calcBalance(AVLNode p){int left_depth;int right_depth;//左子树深度if (p.left != null){left_depth = p.left.depth;}else {left_depth = 0;}//右子树深度if (p.right != null){right_depth = p.right.depth;}else {right_depth = 0;}return left_depth - right_depth;}

    public int calcDepth(AVLNode p){int depth = 0;if (p.left != null){depth = p.left.depth;}if (p.right != null && depth < p.right.depth){depth = p.right.depth;}depth++;return depth;}