public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
        ArrayList<Integer> res=new ArrayList<>();
        if (root==null){
            return res;
        }

        ArrayList<TreeNode> queue=new ArrayList<>();

        queue.add(root);

        while (queue.size()!=0){
            TreeNode currNode= queue.remove(0);
            res.add(currNode.val);

            if (currNode.left!=null){
                queue.add(currNode.left);
            }
            if (currNode.right!=null){
                queue.add(currNode.right);
            }
        }
        return res;
    }

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

public class LevelPrint {
    public static class Node {
        public int value;
        public Node left;
        public Node right;

        public Node(int data) {
            this.value = data;
        }
    }
    
    public  static void  levelPrint(Node head){
        System.out.println("按层打印结果: ↓");
        if (head==null){
            return;
        }
        Queue<Node> queue=new LinkedList<>();
        queue.offer(head);
        while (!queue.isEmpty()){
            head=queue.poll();
            System.out.print(head.value+"  ");
            if (head.left!=null){
                queue.offer(head.left);
            }
            if (head.right!=null){
                queue.offer(head.right);
            }
        }
    }


    public static void main(String[] args){
        Node head = new Node(5);
        head.left = new Node(3);
        head.right = new Node(8);
        head.left.left = new Node(2);
        head.left.right = new Node(4);
        head.left.left.left = new Node(1);
        head.right.left = new Node(7);
        head.right.left.left = new Node(6);
        head.right.left.left.left = new Node(1151);
        head.right.right = new Node(10);
        head.right.right.left = new Node(9);
        head.right.right.right = new Node(11);
        levelPrint(head);
    }


}