6、二叉树树（java实现）

1、创建树的节点

public class Node {
    public Object data;           //存储数据
    public Node leftChild;        //左子树指针
    public Node rightChild;       //右字树指针
}

2、二叉树的实现

public class BinTree {
    Node node;

    public BinTree() {
    }

    public BinTree(Node node) {
        node.leftChild = node.leftChild;
        node.rightChild = node.rightChild;
    }

    /**
     * 初始化二叉树头结点
     *
     * @param node ：头结点
     */
    public void initBinTree(Node node) {
        node.leftChild = null;
        node.rightChild = null;
    }

    /**
     * 左插入节点
     *
     * @param curr_node
     * @param element
     * @return
     */
    public Node insertLeftChild(Node curr_node, Object element) {
        if (curr_node == null) {
            return null;
        }

        Node newnode = new Node(); //初始化新节点
        newnode.data = element;
        newnode.leftChild = curr_node.leftChild; //插入新节点左子树为原子树node的左子树（---> null）
        newnode.rightChild = null;

        curr_node.leftChild = newnode; //转换curr_node节点为当前插入后的左子树
        return curr_node.leftChild;
    }

    /**
     * 右插入节点
     *
     * @param curr_node
     * @param element
     * @return
     */
    public Node insertRightChild(Node curr_node, Object element) {
        if (curr_node == null) {
            return null;
        }

        Node saveNode = curr_node.rightChild;

        Node newNode = new Node();
        newNode.data = element;
        newNode.rightChild = newNode;
        newNode.rightChild = null;

        curr_node.rightChild = newNode;
        return curr_node.rightChild;
    }

    /**
     * 删除左子树
     *
     * @param currNode
     * @return
     */
    public Node deleteLeftChild(Node currNode) {
        if (currNode == null || currNode.leftChild == null) {
            return null;
        }
        currNode.leftChild = null;
        return currNode;
    }

    /**
     * 删除右节点
     *
     * @param currNode
     * @return
     */
    public Node deleteRightChild(Node currNode) {
        if (currNode == null || currNode.rightChild == null) {
            return null;
        }
        currNode.rightChild = null;
        return currNode;
    }

    /**
     * 前序遍历
     *
     * @param root
     */
    public void preOrder(Node root) {
        if (root != null) {
            System.out.print(root.data + " ");
            preOrder(root.leftChild);
            preOrder(root.rightChild);
        }
    }

    /**
     * 中序遍历
     *
     * @param root
     */
    public void inOrder(Node root) {
        if (root != null) {
            inOrder(root.leftChild);
            System.out.print(root.data + " ");
            inOrder(root.rightChild);
        }
    }

    /**
     * 后序遍历
     *
     * @param root
     */
    public void postOrder(Node root) {
        if (root != null) {
            postOrder(root.leftChild);
            postOrder(root.rightChild);
            System.out.print(root.data + " ");
        }
    }

    /**
     * 打印二叉树
     *
     * @param root
     * @param n
     */
    public void printf(Node root, int n) {

        if (root == null) {   //为空判断
            return;
        }
        printf(root.rightChild, n + 1);  //遍历打印右子树

        for (int i = 0; i < n - 1; i++) {
            System.out.print("\t");
        }

        if (n > 0) {
            System.out.println("----" + root.data);
        }
        printf(root.leftChild, n + 1);
    }

    /**
     * 二叉树查找元素
     * @param root
     * @param x
     * @return
     */
    public Node search(Node root, Object x) {
        Node findNode = null;   //找到就返回该节点指针，找不到就返回空

        if (root != null) {
            if (root.data == x) {
                findNode = root;
            } else {
                findNode = search(root.leftChild, x);
                if (findNode == null) {
                    findNode = search(root.rightChild, x);
                }
            }
        }
        return findNode;
    }




    public static void main(String[] args) {

        Node root = new Node();
        root.leftChild = null;
        root.rightChild = null;

        BinTree binTree = new BinTree();

        Node p = null;

        p = binTree.insertLeftChild(root, 'A');
        p = binTree.insertLeftChild(p, 'B');
        p = binTree.insertLeftChild(p, 'D');
        p = binTree.insertRightChild(p, 'G');
        p = binTree.insertRightChild(root.leftChild, 'C');
        binTree.insertLeftChild(p, 'E');
        binTree.insertRightChild(p, 'F');


        binTree.printf(root, 0);

        System.out.print("前序遍历 ");
        binTree.preOrder(root.leftChild);
        System.out.println();

        System.out.print("中序遍历 ");
        binTree.inOrder(root.leftChild);
        System.out.println();

        System.out.print("后序遍历 ");
        binTree.postOrder(root.leftChild);
        System.out.println();
        
        Node findNode = binTree.search(root,'E');
        if (findNode == null){
            System.out.println("没有找到E");
        }else{
            System.out.println("元素E在二叉树中");
        }

        System.out.println("删除元素E");
        binTree.deleteLeftChild(p);
        
        Node findE = binTree.search(root,'E');
        if (findE == null){
            System.out.println("没有找到E");
        }else{
            System.out.println("元素E在二叉树中");
        }

    }
}

3、实现结果

        ----F
    ----C
        ----E
----A
    ----B
            ----G
        ----D
前序遍历 A B D G C E F 
中序遍历 D G B A E C F 
后序遍历 G D B E F C A 
元素E在二叉树中
删除元素E
没有找到E