java二叉排序樹

　　二叉排序樹又稱二叉查找樹。它或者是一顆空樹，或者是具有如下性質的二叉樹：

　　1.如果左子樹不空，那么左子樹上的所有節點均小於它的根節點的值；

　　2.如果右子樹不空，那么右子樹上的所有節點均大於它的根節點的值；

　　3.左右字樹也分別是二叉排序樹。

　　關於二叉排序樹的建立和遍歷的代碼實現如下：

  class Node{
    public int data;
    public Node left;
    public Node right;
    public Node(int data){
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

public class BinaryTree{
    
    private Node root;
    public BinaryTree(){
        root = null;
    }

    //將date插入到排序二叉樹中
    public void insert(int data){
        Node newNode = new Node(data);
        if(root == null)
            root = newNode;
        else{
            Node current = root;
            Node parent;
            while (true) {    //尋找插入的位置
                parent = current;
                if(data < current.data){
                    current = current.left;
                    if(current == null){
                        parent.left = newNode;
                        return;
                    }
                }
                else{
                    current = current.right;
                    if(current == null){
                        parent.right = newNode;
                        return;
                    }
                }
            }
        }
    }
    //輸入數值，構建二叉樹
    public void buildTree(int[] data){
        for (int i = 0; i<data.length; i++) {
            insert(data[i]);
        }
    }
    //中序遍歷方法遞歸實現
    public void inOrder(Node localRoot){
        if (localRoot != null) {
            inOrder(localRoot.left);
            System.out.print(localRoot.data + " ");
            inOrder(localRoot.right);
        }
    }
    public void inOrder(){
        this.inOrder(this.root);
    }
    //先序遍歷方法遞歸實現
    public void preOrder(Node localRoot){
        if (localRoot != null) {
            System.out.print(localRoot.data + " ");
            preOrder(localRoot.left);
            preOrder(localRoot.right);
        }
    }
    public void preOrder(){
        this.preOrder(this.root);
    }
    //后序遍歷方法遞歸實現
    public void postOrder(Node localRoot){
        if (localRoot != null) {
            postOrder(localRoot.left);
            postOrder(localRoot.right);
            System.out.print(localRoot.data + " ");
        }
    }
    public void postOrder(){
        this.postOrder(this.root);
    }
    
    //層次遍歷（利用一個隊列實現）
    public static void levelOrder(Node localRoot){  
        if(localRoot == null)
          return;  
        List<Node> queue = new LinkedList<Node>();  
        queue.add(localRoot);  
        while(!queue.isEmpty()){  
            Node temp = queue.poll(0);  
            System.out.print(temp.data + " ");  
            if(temp.left != null){  
                queue.add(temp.left);  
            }  
            if(temp.right != null){  
                queue.add(temp.right);  
            }  
        }  
        System.out.println();  
    }
    public void levelOrder(){
        this.levelOrder(this.root);
    }
}