樹 的資料結構

public class TreeNode {
    private int data;
    private TreeNode LeftNode;
    private TreeNode RightNode;

    public TreeNode() {
        // TODO Auto-generated constructor stub
    }
    public TreeNode(int data,TreeNode left,TreeNode right) {
        this.data=data;
        this
 
.LeftNode=left;
        this.RightNode=right;
    }

    public int getData() {
        return data;
    }
    public void setData(int data) {
        this.data = data;
    }
    public TreeNode getLeftNode() {
        return LeftNode;
    }
    public void setLeftNode(TreeNode leftNode) {
        LeftNode = leftNode;
    }
    public
 
 TreeNode getRightNode() {
        return RightNode;
    }
    public void setRightNode(TreeNode rightNode) {
        RightNode = rightNode;
    }
}

基本操作

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;


public class shujuJiegou {

    //遞迴前序遍歷
    public void preOrder
 
(TreeNode root) {
        if(root!=null)
        {
            System.out.print(root.getData()+" ");
            preOrder(root.getLeftNode());
            preOrder(root.getRightNode());
        }
    }
    //非遞迴前序
    public void preOrderNoDigui(TreeNode root) {
        Stack<TreeNode> stack=new Stack<>();
        while (true) {
            while (root!=null) {
                System.out.print(root.getData()+" ");
                stack.push(root);
                root=root.getLeftNode();
            }
            if(stack.isEmpty())
                break;
            root=stack.pop();
            root=root.getRightNode();
        }
    }
    //遞迴中序
    public void inOrder(TreeNode root) {
        if(root!=null) {
            inOrder(root.getLeftNode());
            System.out.print(root.getData()+" ");
            inOrder(root.getRightNode());
        }
    }
    //非遞迴中序
    public void inOrderNoDigui(TreeNode root) {
        Stack<TreeNode> stack=new Stack<>();
        while (true) {
            while (root!=null) {
                stack.push(root);
                root=root.getLeftNode();
            }
            if(stack.isEmpty())
                break;
            root=stack.pop();
            System.out.print(root.getData()+" ");
            root=root.getRightNode();
        }
    }
    //遞迴後序
    public void deOrder(TreeNode root) {
        if (root!=null) {
            deOrder(root.getLeftNode());
            deOrder(root.getRightNode());
            System.out.print(root.getData()+" ");
        }
    }
    //非遞迴後序
    public void deOrderNoDigui(TreeNode root) {
        Stack<TreeNode> stack=new Stack<>();
        while (true) {
            if(root!=null) {
                stack.push(root);
                root=root.getLeftNode();
            }else {
                if(stack.isEmpty())
                    return;
                if(stack.lastElement().getRightNode()==null) {
                    root=stack.pop();
                    System.out.print(root.getData()+" ");
                    while (root==stack.lastElement().getRightNode()) {
                        System.out.print(stack.lastElement().getData()+" ");
                        root=stack.pop();
                        if(stack.isEmpty())
                            break;
                    }
                }
                if(!stack.isEmpty())
                    root=stack.lastElement().getRightNode();
                else {
                    root=null;
                }
            }

        }
    }
    //層次遍歷
    public void levelOrder(TreeNode root) {
        TreeNode temp;
        Queue<TreeNode> queue=new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            temp=queue.poll();
            System.out.print(temp.getData()+" ");
            if(temp.getLeftNode()!=null) {
                queue.offer(temp.getLeftNode());
            }
            if(temp.getRightNode()!=null) {
                queue.offer(temp.getRightNode());
            }
        }
    }
    public static void main(String[] args) {
        TreeNode node10=new TreeNode(10,null,null);
        TreeNode node8=new TreeNode(8,null,null);
        TreeNode node9=new TreeNode(9,null,node10);
        TreeNode node4=new TreeNode(4,null,null);
        TreeNode node5=new TreeNode(5,node8,node9);
        TreeNode node6=new TreeNode(6,null,null);
        TreeNode node7=new TreeNode(7,null,null);
        TreeNode node2=new TreeNode(2,node4,node5);
        TreeNode node3=new TreeNode(3,node6,node7);
        TreeNode node1=new TreeNode(1,node2,node3);

        shujuJiegou tree=new shujuJiegou();
        System.out.println("------前序遍歷-------");
        tree.preOrder(node1);
        System.out.println();
        tree.preOrderNoDigui(node1);
        System.out.println();

        System.out.println("------中序遍歷-------");
        tree.inOrder(node1);
        System.out.println();
        tree.inOrderNoDigui(node1);
        System.out.println();

        System.out.println("------後序遍歷-------");
        tree.deOrder(node1);
        System.out.println();
        tree.deOrderNoDigui(node1);
        System.out.println();

        System.out.println("------層次遍歷-------");
        tree.levelOrder(node1);
        System.out.println();
        tree.levelOrder(node1);
        System.out.println();
    }
}