平衡二叉树（AVL）Java

1066 Root of AVL Tree (25 分)

import java.util.Scanner;

/**
 * @author RabbiT
 * 1066 Root of AVL Tree (25 分)
 */
public class Main01 {

    /**
     * 树节点类
     */
    public static class TreeNode{
        int value;
        int depth;
        TreeNode left;
        TreeNode right;

        TreeNode(int value){
            this.value = value;
            this.depth = 1;
            this.left = null;
            this.right = null;
        }
    }

    /**
     * 获取当前树节点的高度
     * @param root
     * @return
     */
    public int getDepth(TreeNode root){
        if(root == null){
            return 0;
        }
        return root.depth;
    }

    /**
     * 获取当前树节点的平衡因子 五种情况
     * @param root
     * @return
     */
    public int getBalanceFactor(TreeNode root){
        if(root == null){
            return 0;
        }
        if(root.left == null && root.right == null){
            return 0;
        }else if(root.left == null){
            return -getDepth(root.right);
        }else if(root.right == null){
            return getDepth(root.left);
        }else{
            return getDepth(root.left) - getDepth(root.right);
        }
    }

    /**
     * 调整后的树需要更新节点的最新深度
     * @param root
     */
    public void updateDepth(TreeNode root){
        if(root.left == null && root.right == null){
            root.depth = 1;
        }else if(root.right == null){
            root.depth = getDepth(root.left) + 1;
        }else if(root.left == null){
            root.depth = getDepth(root.right) + 1;
        }else{
            root.depth = Math.max(getDepth(root.left),getDepth(root.right)) + 1;
        }
    }

    /**
     * 当遇到节点平衡因子为负数时 -1 -2 需要左旋
     * @param root
     * @return
     */
    public TreeNode leftCircle(TreeNode root){
        TreeNode temp = root.right;
        root.right = temp.left;
        temp.left = root;
        updateDepth(root);
        updateDepth(temp);
        root = temp;
        return root;
    }

    /**
     * 当遇到节点平衡因子为正数时 1 2 需要右旋
     * @param root
     * @return
     */
    public TreeNode rightCircle(TreeNode root){
        TreeNode temp = root.left;
        root.left = temp.right;
        temp.right = root;
        updateDepth(root);
        updateDepth(temp);
        root = temp;
        return root;
    }

    /**
     * 和二叉搜索树一致
     * @param root
     * @param value
     * @return
     */
    public boolean search(TreeNode root,int value){
        if(root == null){
            return false;
        }
        if(value == root.value){
            return true;
        }else if(value < root.value){
            return search(root.left,value);
        }else{
            return search(root.right,value);
        }
    }

    /**
     * 二叉平衡树进行插入节点操作 需要调整
     * @param root
     * @param node
     * @return
     */
    public TreeNode insert(TreeNode root,TreeNode node){
        if(root.value > node.value){
            if(root.left == null){
                root.left = node;
            }else{
                root.left = insert(root.left,node);
            }
        }else{
            if(root.right == null){
                root.right = node;
            }else{
                root.right = insert(root.right,node);
            }
        }
        updateDepth(root);
        root = adjustBalance(root);
        return root;
    }

    /**
     * 平衡因子为 2 -2需要调整二叉树
     * @param root
     * @return
     */
    public TreeNode adjustBalance(TreeNode root) {
        //为正数 则是L型 有LL LR两种
        if(getBalanceFactor(root) == 2){
            if(getBalanceFactor(root.left) == 1){
                root = rightCircle(root);
            }else if(getBalanceFactor(root.left) == -1){
                root.left = leftCircle(root.left);
                root = rightCircle(root);
            }
        }else if(getBalanceFactor(root) == -2){
            if(getBalanceFactor(root.right) == -1){
                root = leftCircle(root);
            }else if(getBalanceFactor(root.right) == 1){
                root.right = rightCircle(root.right);
                root = leftCircle(root);
            }
        }
        return root;
    }

    public TreeNode createTree(TreeNode[] treeArr){
        TreeNode root = treeArr[0];
        for(int i = 1;i<treeArr.length;i++){
            root = insert(root,treeArr[i]);
        }
        return root;
    }

    public static void main(String[] args) {
        Main01 main = new Main01();
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        TreeNode[] treeArr = new TreeNode[n];
        for(int i = 0;i<n;i++){
            treeArr[i] = new TreeNode(sc.nextInt());
        }
        TreeNode root = main.createTree(treeArr);
        System.out.println(root.value);
        System.out.println(root.left.value);
        System.out.println(root.right.value);
    }
}