平衡二叉树实现（Java）_二叉平衡树画java

终于搞出来了！！！等以后有时间再来写详细过程。。。

import java.util.*;
public class AVLTree {
    private TreeNode root;
    private class TreeNode{
        int val;
        int height;
        int balance;
        TreeNode parent;
        TreeNode left;
        TreeNode right;
        public TreeNode(){}
        public TreeNode(int val){
            this.val = val;
            height = 1;
        }
    }
    private int getHeight(TreeNode p){
        if(p==null){
            return 0;
        }else{
            return p.height;
        }
    }
    private void left_rotate(TreeNode p){
        if(p!=null){
            TreeNode r = p.right;
            p.right = r.left;
            if(r.left!=null) r.left.parent = p;
            r.parent = p.parent;
            if(p.parent==null)
                root = r;
            else if(p.parent.left == p)
                p.parent.left = r;
            else
                p.parent.right = r;
            r.left = p;
            p.parent = r;
            updateNode(p);
            updateNode(r);
        }
    }
    private void right_rotate(TreeNode p){
        if(p!=null){
            TreeNode l = p.left;
            p.left = l.right;
            if(l.right!=null) l.right.parent=p;
            l.parent = p.parent;
            if(p.parent==null)
                root = l;
            else if(p.parent.left == p)
                p.parent.left = l;
            else
                p.parent.right = l;
            l.right = p;
            p.parent = l;
            updateNode(p);
            updateNode(l);
        }
    }
    //更新父子节点关系
    private void updateChild(TreeNode parent,TreeNode root,TreeNode p){
        if(parent==null){
            this.root = p;
        }else if(parent.left == root){
            parent.left = p;
        }else{
            parent.right = p;
        }
    }
    //更新节点的高度和平衡因子
    private void updateNode(TreeNode p){
        p.height = Math.max(getHeight(p.left),getHeight(p.right))+1;
        p.balance = getHeight(p.left)-getHeight(p.right);
    }
    //添加一个节点
    public void add(int val){
        if(this.root==null){
            this.root = new TreeNode(val);
        }else{
            TreeNode p = new TreeNode(val);
            insert(this.root,p);
        }
    }
    //删除一个节点
    public void delete(int val){
        remove(this.root,val);
    }
    private void remove(TreeNode root,int val){
        if(root==null) return ;
        TreeNode parent;
        while(root!=null){
            if(root.val==val){       //如果当前节点即为要删除的节点
                parent = root.parent;
                if(parent==null){	  //首先根据parent是否为空判断是否是根节点
                    if(root.left == null){	//根的左儿子为空，将右儿子赋值为根节点
                        this.root = root.right;
                    }else if(root.right == null){ //根的右儿子为空，将左儿子赋值为根节点
                        this.root = root.left;
                    }else{		//左右子树均不为空，指定右儿子为根节点，将左子树加入到右子树中
                        this.root = root.right;
                        this.root.parent = null;
                        insert(this.root,root.left);
                    }
                }else{	//如果不是根节点
                    if(root.left==null){  //左儿子为空，将右儿子与父节点关联
                        updateChild(parent,root,root.right);
                        balance(parent);
                    }else if(root.right==null){//右儿子为空，将左儿子与父节点关联
                        updateChild(parent,root,root.left);
                        balance(parent);
                    }else{	//左右儿子均不为空，将右儿子与父节点关联，并将左子树插入到右子树中
                        updateChild(parent,root,root.right);
                        insert(root.right,root.left);
                        balance(root.left);
                    }
                }
                return ;
            }else if(val<root.val){
                root = root.left;
            }else{
                root = root.right;
            }
        }
    }
    private void insert(TreeNode root,TreeNode newNode){
        if(newNode.val<root.val){  //新节点值小于root节点值，向左子树查找
            if(root.left==null){
                root.left = newNode;
                newNode.parent = root;
                balance(root);
            }else{
                insert(root.left,newNode);
            }
        }else if(newNode.val>root.val){  //新节点值大于root节点值，向右子树查找
            if(root.right==null){
                root.right = newNode;
                newNode.parent = root;
                balance(root);
            }else{
                insert(root.right,newNode);
            }

        }
    }
    //平衡该二叉树
    private void balance(TreeNode root){
        while(root!=null){
            updateNode(root);
            if(root.balance<=-2){  
                if(root.right.balance==1){ //如果是右左不平衡，则先右旋
                    right_rotate(root.right);
                }
                left_rotate(root);
            }else if(root.balance>=2){ 
                if(root.left.balance==-1){  //如果是左右不平衡，则先左旋
                    left_rotate(root.left);
                }
                right_rotate(root);
            }
            root = root.parent;
        }
    }
    public void print(){
        System.out.print("Print Tree: ");
        levelOrder(this.root);
        System.out.println();
    }
    //层次遍历算法
    private void levelOrder(TreeNode root){
        LinkedList<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while(!queue.isEmpty()){
            TreeNode p = queue.removeFirst();
            if(p==null){
                System.out.print(" @ ");
            }else{
                System.out.print(" " + p.val + " ");
                queue.add(p.left);
                queue.add(p.right);
            }
        }
    }
    public static void main(String[] args) {
        AVLTree t = new AVLTree();
        int arr[] = {10,20,18,5,8};
//        for(int i=0;i<arr.length;i++)
//        {
//            t.add(arr[i]);
//        }
        for(int i=0;i<30;i++)
        {
            t.add(i);
        }

        t.delete(1);
        t.print();
    }
}

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