using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace SuanfapRractice
{public class TreeNode{public int data;public TreeNode leftChild;public TreeNode rightChild;public TreeNode(int data){this.data = data;}}
}
using System.Collections;
using System.Collections.Generic;
using System.Numerics;
using System.Reflection.Metadata.Ecma335;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System;
using System.Collections.Generic;
using System.Xml.Linq;
using SuanfapRractice;
using System.Linq;public class Solution
{public static void Main(String[] args){TreeNode root = new TreeNode(3);root.leftChild = new TreeNode(9);root.rightChild = new TreeNode(20);root.rightChild.leftChild = new TreeNode(15);root.rightChild.rightChild = new TreeNode(7);LevelOrder(root);}public static int[] LevelOrder(TreeNode root){if (root == null){return new int[0];}Queue queue = new Queue();queue.Enqueue(root);List res = new List();while (queue.Count > 0){TreeNode node = queue.Dequeue();res.Add(node.data);if (node.leftChild != null){queue.Enqueue(node.leftChild);}if (node.rightChild != null){queue.Enqueue(node.rightChild);}}// 使用foreach LINQ方法res.ForEach(num => Console.WriteLine(num + ", "));//打印return res.ToArray();}