从上到下逐行遍历C#中的树

using System;
using System.Collections.Generic;

public class TreeNode
{
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode(int val = 0, TreeNode left = null, TreeNode right = null)
    {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

public class TreeTraversal
{
    public static void LevelOrderTraversal(TreeNode root)
    {
        if (root == null)
            return;

        Queue<TreeNode> queue = new Queue<TreeNode>();
        queue.Enqueue(root);

        while (queue.Count > 0)
        {
            TreeNode node = queue.Dequeue();
            Console.Write(node.val + " ");

            if (node.left != null)
                queue.Enqueue(node.left);

            if (node.right != null)
                queue.Enqueue(node.right);
        }
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        // 构建一个示例树
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(3);
        root.left.left = new TreeNode(4);
        root.left.right = new TreeNode(5);

        // 从上到下逐行遍历树
        TreeTraversal.LevelOrderTraversal(root);
    }
}