二叉查找树的各种操作(插入、删除、查找、遍历)

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二叉查找树主要的特点:当前节点左边的所有节点要小于该节点,右边的要大于该节点。(不能只判断当前节点的左儿子和右儿子是否小于或大于当前节点)

下面是对二叉查找树的各种操作列表
1. 插入(递归、非递归)
2. 删除
3. 查找最小值、最大值
4. 先序遍历(递归,非递归)
5. 中序遍历(递归,非递归)
6. 后序遍历(递归,非递归)
7. 层次遍历
8. 检查二叉树是否二叉查找树(时间复杂度O(nlogn)和O(n))

节点类代码:

import java.util.Queue;import java.util.Stack;import java.util.concurrent.LinkedBlockingDeque;/** * * @author fx50jk * @param <T> */class BinaryTree<Key extends Comparable<Key>, T> {    TreeNode root;    public class TreeNode {        public TreeNode leftchild;        public TreeNode rightchild;        public Key key;        public T data;        public boolean visited = false;        public TreeNode() {        }        public TreeNode(Key key, T data) {            this.key = key;            this.data = data;        }        public TreeNode(T data, TreeNode leftchild, TreeNode rightchild) {            this.leftchild = leftchild;            this.rightchild = rightchild;            this.data = data;        }    }    public BinaryTree(TreeNode root) {        this.root = root;    }    public BinaryTree() {    }    public void insert1(Key key) {        if (key == null) {            System.out.println("???");        } else {            root = insert1(root, key);        }    }    private TreeNode insert1(TreeNode rootNode, Key key) {        if (rootNode == null) {            rootNode = new TreeNode();            rootNode.key = key;        }        //插入左子树还是右子树        int comRes = key.compareTo(rootNode.key);        if (comRes < 0) {            rootNode.leftchild = insert1(rootNode.leftchild, key);        } else if (comRes > 0) {            rootNode.rightchild = insert1(rootNode.rightchild, key);        } else {             //已经有该数据            System.out.println("键值重复");        }        return rootNode;    }    public void insert(Key key, T value) {        if (root == null) {            root = new TreeNode(key, value);            return;        }        TreeNode currentNode = root;        TreeNode parentNode = root;        boolean isLeftChild = true;        while (currentNode != null) {            parentNode = currentNode;//保存父节点的信息            //判断它是左节点还是右节点            int comRes = key.compareTo(currentNode.key);            if (comRes < 0) {                currentNode = currentNode.leftchild;                isLeftChild = true;            } else {                currentNode = currentNode.rightchild;                isLeftChild = false;            }        }        TreeNode newNode = new TreeNode(key, value);        if (isLeftChild) {            parentNode.leftchild = newNode;        } else {            parentNode.rightchild = newNode;        }    }    //根据key删除节点    public void remove(Key key){        root=remove(root,key);    }    private TreeNode remove(TreeNode rootNode,Key key){        if (rootNode==null) {            return rootNode;        }        int comRes=key.compareTo(rootNode.key);        if (comRes<0) {            rootNode.leftchild=remove(rootNode.leftchild, key);        }else if(comRes>0){            rootNode.rightchild=remove(rootNode.rightchild, key);        }else if(rootNode.leftchild!=null&&rootNode.rightchild!=null){//已找到该节点,开始进行删除            rootNode.key=findMin(rootNode.rightchild).key;            rootNode.rightchild=remove(rootNode.rightchild, key);        }else{            rootNode=(rootNode.leftchild!=null)?rootNode.leftchild:rootNode.rightchild;        }        return rootNode;    }    //查找最小值    public Key findMin(){        if (root==null) {            return null;        }        return findMin(root).key;    }    private TreeNode findMin(TreeNode rootNode){        if (rootNode==null) {            return null;        }else if(rootNode.leftchild==null){//从左子树中找最左的节点            return rootNode;        }else{           return  findMin(rootNode.leftchild);        }    }        //查找最大值    public Key findMax(){        if (root==null) {            return null;        }        return findMax(root).key;    }    private TreeNode findMax(TreeNode rootNode){        if (rootNode==null) {            return null;        }else if(rootNode.rightchild==null){//从右子树中找最右的节点            return rootNode;        }else{           return  findMin(rootNode.rightchild);        }    }    //遍历的递归实现    //先序遍历    public void preOrder() {        preOrder(root);        System.out.println("");    }    private void preOrder(TreeNode treeNode) {        if (treeNode != null) {            System.out.print(treeNode.key + "\t");            preOrder(treeNode.leftchild);            preOrder(treeNode.rightchild);        }    }    //中序遍历    public void midOrder() {        midOrder(root);        System.out.println("");    }    private void midOrder(TreeNode treeNode) {        if (treeNode != null) {            midOrder(treeNode.leftchild);            System.out.print(treeNode.key + "\t");            midOrder(treeNode.rightchild);        }    }    //后序遍历    public void postOrder() {         postOrder(root);    }    private void postOrder(TreeNode treeNode) {        if (treeNode != null) {            postOrder(treeNode.leftchild);            postOrder(treeNode.rightchild);            System.out.print(treeNode.key + "\t");        }    }    //遍历的非递归实现    public void preOrderTraverse() {        Stack<TreeNode> stack = new Stack<>();        TreeNode rootNode = root;        if (rootNode != null) {            stack.push(rootNode);            while (!stack.isEmpty()) {                rootNode = stack.pop();                System.out.print(rootNode.key + "\t");                if (rootNode.rightchild != null) {                    stack.push(rootNode.rightchild);                }                if (rootNode.leftchild != null) {                    stack.push(rootNode.leftchild);                }            }        }        System.out.println("");    }    public void inOrderTraverse() {        Stack<TreeNode> stack = new Stack<>();        TreeNode rootNode = root;        while (rootNode != null) {            while (rootNode != null) {                if (rootNode.rightchild != null) {                    stack.push(rootNode.rightchild);//先让右节点入栈                }                stack.push(rootNode);//让中间节点入栈                rootNode = rootNode.leftchild;            }            rootNode = stack.pop();            while (!stack.isEmpty() && rootNode.rightchild == null) {                System.out.print(rootNode.key + "\t");                rootNode = stack.pop();            }            System.out.print(rootNode.key + "\t");            if (!stack.empty()) {                rootNode = stack.pop();            } else {                rootNode = null;            }        }        System.out.println("");    }    public void postOrderTraverse() {        TreeNode rootNode = root;        TreeNode temp = root;        Stack<TreeNode> stack = new Stack<>();        while (rootNode != null) {            //左子树入栈            while (rootNode.leftchild != null) {                stack.push(rootNode);                rootNode = rootNode.leftchild;            }            // 当前结点无右子结点或右子结点已经输出              while (rootNode != null && (rootNode.rightchild == null || rootNode.rightchild == temp)) {                System.out.print(rootNode.key + "\t");                temp = rootNode;                if (stack.isEmpty()) {                    return;                }                rootNode = stack.pop();            }            //处理右节点            stack.push(rootNode);            rootNode = rootNode.rightchild;        }        System.out.println("");    }    public void levelOrder() {        /**         * 存放需要遍历的结点,左结点一定优先右节点遍历         */        Queue<TreeNode> queue = new LinkedBlockingDeque<>();        TreeNode rootNode = this.root;        while (rootNode != null) {            //记录经过的结点            System.out.print(rootNode.key + "\t");            //先按层次遍历结点,左结点一定在右结点之前访问            if (rootNode.leftchild != null) {                //孩子结点入队                queue.add(rootNode.leftchild);            }            if (rootNode.rightchild != null) {                queue.add(rootNode.rightchild);            }            //访问下一个结点            rootNode = queue.poll();        }    }    //检查二叉树是否是二叉查找树  时间复杂度为O(NlogN)    public boolean isBalanced(){        return isBalanced(root);    }    private boolean isBalanced(TreeNode rootNode){        if (rootNode==null) {            return true;        }        int heightDiff=getHeight(rootNode.leftchild)-getHeight(rootNode.rightchild);        if (Math.abs(heightDiff)>1) {            return false;        }else{            return isBalanced(rootNode.leftchild)&&isBalanced(rootNode.rightchild);        }    }    public int getHeight(TreeNode rootNode){        if(rootNode==null){            return 0;        }        return Math.max(getHeight(rootNode.leftchild), getHeight(rootNode.rightchild))+1;    }    //判断是否平衡 时间复杂度为O(n)    private int checkHeight(TreeNode rootNode){        if (rootNode==null) {            return 0;        }        //检查左子树是否平衡        int leftHeight=checkHeight(rootNode.leftchild);        if (leftHeight==-1) {            return -1;        }        //检查右子树        int rightHeight=checkHeight(rootNode.rightchild);        if (rightHeight==-1) {            return -1;        }        //检查当前节点是否平衡        int heightDiff=Math.abs(leftHeight-rightHeight);        if (heightDiff>1) {            return -1;        }else{            return Math.max(leftHeight,rightHeight)+1;        }    }    public boolean isBalanced1(){        return checkHeight(root) != -1;    }    /**     * @return the root     */    public TreeNode getRoot() {        return root;    }}

测试类代码 :

public class Test {    /**     * @param args the command line arguments     */    public static void main(String[] args) {        // TODO code application logic here        BinaryTree binaryTree=new BinaryTree();        binaryTree.insert(1,2);        binaryTree.insert(3,4);        binaryTree.insert(7,6);        binaryTree.insert(4,8);        binaryTree.insert(5,9);        System.out.println(binaryTree.getRoot().key);        System.out.print("前序遍历(递归):"+"\t");        binaryTree.preOrder();        System.out.print("中序遍历(递归):"+"\t");        binaryTree.midOrder();        System.out.print("后序遍历(递归):"+"\t");        binaryTree.postOrder();          System.out.print("\n前序遍历(非递归):"+"\t");        binaryTree.preOrderTraverse();        System.out.print("中序遍历(非递归):"+"\t");        binaryTree.inOrderTraverse();        System.out.print("后序遍历(非递归):"+"\t");        binaryTree.postOrderTraverse();        System.out.print("\n层次遍历(非递归):"+"\t");        binaryTree.levelOrder();    }}
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