---------手撕二叉树，完成二叉树的前中后序遍历，以及前中后序查找

注意：在进行查找时，利用一个临时结点的思想来判断是否找到。

package ShangGuiGu.Tree;

public class BinaryTreeDemo {
    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        HeroNode root = new HeroNode(1,"宋江");
        HeroNode node1 = new HeroNode(2,"吴用");
        HeroNode node2 = new HeroNode(3,"卢俊义");
        HeroNode node3 = new HeroNode(4,"林冲");
        HeroNode node4 = new HeroNode(5,"关胜");

        binaryTree.setRoot(root);
        root.setLeft(node1);
        root.setRight(node2);
        node2.setLeft(node3);
        node2.setRight(node4);

        System.out.println("前序遍历");
        binaryTree.preOrder();

        System.out.println("中序遍历");
        binaryTree.infixOrder();

        System.out.println("后序遍历");
        binaryTree.postOrder();

        System.out.println("前序遍历方式");
        HeroNode resNode = binaryTree.preOrderSearch(5);
        if(resNode != null){
            System.out.println(resNode.toString());
        }else{
            System.out.println("未找到");
        }
    }
}

class BinaryTree{
    private HeroNode root;

    public void setRoot(HeroNode root) {
        this.root = root;
    }
    //前中后序遍历
    public void preOrder(){
        if(this.root != null){
            this.root.preOrder();
        } else{
            System.out.println("二叉树为空，无法遍历");
        }
    }

    public void infixOrder(){
        if(this.root != null){
            this.root.infixOrder();
        } else{
            System.out.println("二叉树为空，无法遍历");
        }
    }

    public void postOrder(){
        if(this.root != null){
            this.root.postOrder();
        } else{
            System.out.println("二叉树为空，无法遍历");
        }
    }
    //前中后序遍历查找
    public HeroNode preOrderSearch(int no){
        if(root != null){
            return root.preOrderSearch(no);
        }else{
            return null;
        }
    }

    public HeroNode infixOrderSearch(int no){
        if(root != null){
            return root.infixOrdeeSearch(no);
        }else{
            return null;
        }
    }

    public HeroNode postOrderSearch(int no){
        if(root != null){
            return root.postOrderSearch(no);
        }else{
            return null;
        }
    }
}

class HeroNode{
    private int no;
    private String name;
    private HeroNode left;
    private HeroNode right;
    public HeroNode(int no , String name){
        this.no = no;
        this.name = name;
    }

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public HeroNode getLeft() {
        return left;
    }

    public void setLeft(HeroNode left) {
        this.left = left;
    }

    public HeroNode getRight() {
        return right;
    }

    public void setRight(HeroNode right) {
        this.right = right;
    }

    @Override
    public String toString() {
        return  "HeroNode [no=" + no + ", name=" + name +"]";
    }

    public void preOrder(){
        System.out.println(this); //先输出父节点
        //递归向左子树前序遍历
        if(this.left != null){
            this.left.preOrder();
        }
        if(this.right != null){
            this.right.preOrder();
        }
    }

    public void infixOrder(){
        if(this.left != null){
            this.left.infixOrder();
        }
        System.out.println(this);
        if(this.right != null){
            this.right.infixOrder();
        }
    }

    public void postOrder(){
        if(this.left != null){
            this.left.postOrder();
        }

        if(this.right != null){
            this.right.postOrder();
        }
        System.out.println(this);
    }

    /* 前序遍历查找
    * 查找no
    * 如果找到，就返回该Node，如果没有找到就返回null
    * */
    public HeroNode preOrderSearch(int no){
        //比较当前结点是不是目标值
        if(this.no == no){
            return this;
        }
        //1.判断当前结点的左子节点是否为空，如果不为空，则递归前序查找
        //2.如果左递归前序查找，找到结点，则返回
        HeroNode resNode = null;
        if(this.left != null){
            resNode = this.left.preOrderSearch(no);
        }
        if(resNode != null){
            return resNode;
        }
        //1.判断当前结点的右子节点是否为空，如果不为空，则递归前序查找
        //2.如果右递归前序查找，找到结点，则返回
        if(this.right != null){
            resNode = this.right.preOrderSearch(no);
        }
        return resNode;
    }

    //中序遍历查找
    public HeroNode infixOrdeeSearch(int no){
        HeroNode resNode = null ;
        if(this.left != null){
            resNode = this.left.infixOrdeeSearch(no);
        }
        if(resNode != null){
            return resNode;
        }
        if(this.no == no){
            return this;
        }
        if(this.right != null){
            resNode = this.right.infixOrdeeSearch(no);
        }
        return resNode;
    }

    //后续遍历查找
    public HeroNode postOrderSearch(int no){
        HeroNode resNode = null;
        if(this.left != null){
            resNode = this.left.postOrderSearch(no);
        }
        if(resNode != null){
            return resNode;
        }
        if(this.right != null){
            resNode = this.right.postOrderSearch(no);
        }
        if(resNode != null){
            return resNode;
        }
        if(this.no == no){
            return this;
        }
        return resNode;
    }
}