C#代码创建二叉树以及遍历二叉树

using System;
using System.Collections.Generic;
using System.Text;

namespace BinaryDemo
{
    public class TreeNode
    {
        /*
         * 树的知识点
         * 树结点 根结点 结点子树
         * 结点的度  结点关系 结点层次
         * 树的深度/高度
         */
        //结点下标  结点下标字符串数据 左子树 右子树
        private int index;
        private string data;
        private TreeNode leftChild;
        private TreeNode rightChild;
        private TreeNode parent;


        /// <summary>
        /// 有参构造结点下标  结点下标的字符串数据
        /// </summary>
        /// <param name="index"></param>
        /// <param name="data"></param>
        public TreeNode(int index, string data)
        {
            this.index = index;
            this.data = data;
            this.leftChild = null;
            this.rightChild = null;
        }

        public int getIndex()
        {
            return index;
        }
        public void setIndex(int index)
        {
            this.index = index;
        }
        //拿到左右子串的数据
        public String getData()
        {
            return data;
        }
        public void setData(String data)
        {
            this.data = data;
        }
        //拿到左子树
        public TreeNode getLeftChild()
        {
            return leftChild;
        }
        public void setLeftChild(TreeNode leftChild)
        {
            this.leftChild = leftChild;
        }
        //拿到右子树
        public TreeNode getRightChild()
        {
            return rightChild;
        }
        public void setRightChild(TreeNode rightChild)
        {
            this.rightChild = rightChild;
        }
        public TreeNode getParent()
        {
            return parent;
        }
        public void setParent(TreeNode parent)
        {
            this.parent = parent;
        }
        //快捷键生成的字段get和set
        public int Index { get => index; set => index = value; }
        public string Data { get => data; set => data = value; }
        public TreeNode LeftChild { get => leftChild; set => leftChild = value; }
        public TreeNode RightChild { get => rightChild; set => rightChild = value; }
        public TreeNode Parent { get => parent; set => parent = value; }
    }
}

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

namespace BinaryDemo
{
    public class BinaryTree
    {
        //根结点
        public TreeNode root = null;
        public static string[] str;
        public static int count;
        /// <summary>
        /// 无参构造设置根结点并赋值数据
        /// </summary>
        public BinaryTree()
        {
            root = new TreeNode(1,"A");
        }
        /// <summary>
        /// 构建二叉树的方法    B C D E F
        /// 手动的构建一棵二叉树  很快就可以得出这个二叉树的结构
        /// </summary>
        public void CreateBinaryTree()
        {
            TreeNode nodeb = new TreeNode(2,"B");
            TreeNode nodec = new TreeNode(3, "C");
            TreeNode noded = new TreeNode(4, "D");
            TreeNode nodee = new TreeNode(5, "E");
            TreeNode nodef = new TreeNode(6, "F");
            root.LeftChild = nodeb;
            root.RightChild = nodec;
            nodeb.LeftChild = noded;
            nodeb.RightChild = nodee;
            nodec.RightChild = nodef;
        }
        /// <summary>
        /// 先序遍历 --迭代
        /// 若二叉树为空树直接返回，先序遍历的特点根左右
        /// </summary>
        public void PreOrder(TreeNode node)
        {
            if (node == null)
            {
                return;
            }
            else
            {
                //node.getData()我们可以获取到二叉树的根结点的数据
                Console.WriteLine("先序遍历" + "\t迭代" + node.getData());
                //得到左子树的数据
                PreOrder(node.LeftChild);
                //得到右子树的数据
                PreOrder(node.RightChild);
            }
        }
        /// <summary>
        /// 中序遍历--迭代
        /// 若二叉树为空树直接返回，中序遍历的特点左根右
        /// </summary>
        /// <param name="node"></param>
        public void MidOrder(TreeNode node)
        {
            if (node == null)
            {
                return;
            }
            else
            {
                MidOrder(node.LeftChild);
                Console.WriteLine("中序遍历" + "\t迭代" + node.getData());
                MidOrder(node.RightChild);
            }
        }
        /// <summary>
        /// 后序遍历--迭代
        /// 若二叉树为空树直接返回，中序遍历的特点左右根
        /// </summary>
        /// <param name="node"></param>
        public void LastOrder(TreeNode node)
        {
            if (node == null)
            {
                return;
            }
            else
            {
                LastOrder(node.LeftChild);
                LastOrder(node.RightChild);
                Console.WriteLine("后序遍历" + "\t迭代" + node.getData());
            }
        }
        
        //-----------------------------------分界线------------------------------------------
        
        /*
         迭代与普通循环的区别是：迭代时，循环代码中参与运算的变量同时是保存结果的变量，
         当前保存的结果作为下一次循环计算的初始值。
         
         递归与普通循环的区别是：循环是有去无回，而递归则是有去有回(因为存在终止条件)。
         */
        /// <summary>
        /// 根据先序序列构建二叉树
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public TreeNode CreateBinaryTree(List<String> data)
        {
            return CreateBinaryTree(data.Count, data);
        }
        /// <summary>
        /// 根据先序递归创建二叉树 
        /// "A","B","D","#","#","E","#","#","C","#","F","#","#"
        /// 1、首先判断集合的长度是否为0，为空树或者结点都已经赋值成功
        /// 2、把存储每个结点的集合以及长度传参进来  index为结点下标
        /// 3、先序遍历根左右首先确定根结点也就是集合的第0项，结点下标为0结点数据为A，从集合中删除结点数据
        /// A，现在集合中有12数量
        ///
        /// 4、然后进到获取左子树结点里面，结点B、D一样的执行原理，
        /// 5、注意#的使用   #号代表结点没有左子树或者右子树 一个#代表没有左子树，但是有右子树 两个#左右子
        /// 树都没有
        ///
        /// 6、注意里面的顺序  根结点 左子树  如果出现#号  根据个数判断  一层一层的遍历
        /// </summary>
        /// <param name="count"></param>
        /// <param name="data"></param>
        /// <returns></returns>
        private TreeNode CreateBinaryTree(int count, List<string> data)
        {
            if (data.Count == 0)
            {
                return null;
            }
            string d = data[0];
            
            TreeNode node = null;
            int index = count - data.Count;
            if (d.Equals("#"))
            {
                node = null;
                data.RemoveAt(0);//删除#
                return node;//退出
            }
            
            node = new TreeNode(index,d);//创建新的结点
            if (index == 0)
            {
                root = node;
            }
            data.RemoveAt(0);
            node.LeftChild = CreateBinaryTree(count, data);
            node.RightChild = CreateBinaryTree(count, data);
            return node;
        }

        /// <summary>
        /// 求二叉树的高度
        /// </summary>
        /// <returns></returns>
        public int GetHeight()
        {
            return GetHeight(root);
        }

        private int GetHeight(TreeNode node)
        {
            //根结点为空  高度为0
            if (node == null)
            {
                return 0;
            }
            else
            {
                Console.WriteLine(node.getData());
                //求出左子树和右子树的高度  
                int i = GetHeight(node.LeftChild);
                int j = GetHeight(node.RightChild);
                //左右子树的高度就是树的深度   三目运算符判断哪棵子树的高度高  树的高度就是返回值
                return (i < j) ? j + 1 : i + 1;
            }
        }


        /// <summary>
        /// 获取二叉树的结点数
        /// </summary>
        /// <returns></returns>
        public int GetSize()
        {
            return GetSize(root);
        }

        private int GetSize(TreeNode node)
        {
            //没有根结点即为空树  所以也就不存在结点
            if (node == null)
            {
                return 0;
            }
            else
            {
                //不是空树的情况下  拿到所有的左子树的结点和右子树的结点  最后加上根结点
                return 1 + GetSize(node.LeftChild) + GetSize(node.RightChild);
            }
        }
        

        /// <summary>
        /// 前序遍历-------非迭代
        /// 栈里面的操作A进栈-->B进栈-->D进栈-->D出栈-->B出栈-->E进栈-->E出栈-->A出栈-->C进栈-->C出栈
        ///-->F进栈-->F出栈
        /// </summary>
        /// <param name="root"></param>
        public void TheFirstOrder(TreeNode root)
        {
            Stack<TreeNode> stack = new Stack<TreeNode>();
            TreeNode node = root;
            //结点数不为空或者栈的数量大于0
            while (node != null||stack.Count>0)
            {
                if (node != null)
                {
                    Console.WriteLine("前序遍历"+"非迭代进栈"+node.getData());
                    stack.Push(node);//压栈访问
                    node = node.LeftChild;
                }
                else
                {
                    //弹栈 
                    node = stack.Pop();
                    node=node.RightChild;
                }
            }
        }
        /// <summary>
        /// 中序遍历-------非迭代
        /// </summary>
        /// <param name="root"></param>
        public void TheMidleOrder(TreeNode root)
        {
            Stack<TreeNode> stack = new Stack<TreeNode>();
            TreeNode node = root;
            while (node != null || stack.Count > 0)
            {
                if (node != null)
                {
                    stack.Push(node);//压栈
                    node = node.LeftChild;
                }
                else
                {
                    node = stack.Pop();//弹栈访问
                    Console.WriteLine("中序遍历" + "非迭代出栈" + node.getData());
                    node = node.RightChild;
                }
            }
        }
        /// <summary>
        /// 后序遍历-------非迭代
        /// </summary>
        /// <param name="root"></param>
        public void TheLastOrder(TreeNode root)
        {
            Stack<TreeNode> stack = new Stack<TreeNode>();
            Stack<TreeNode> output = new Stack<TreeNode>();//新建一个中间栈来存储后序遍历的结果
            TreeNode node = root;
            //先序遍历根左右  后序遍历左右根  首先确定根结点  右子树 左子树  反过来就行  
            while (node != null || stack.Count > 0)
            {
                if (node != null)
                {
                    output.Push(node);
                    stack.Push(node);
                    node = node.RightChild;
                }
                else
                {
                    //弹栈
                    node = stack.Pop();
                    node = node.LeftChild;
                }
            }
            while (output.Count > 0)
            {
                Console.WriteLine("后序遍历"+"非迭代"+output.Pop().getData());
            }
        }
    }
}

using System;
using System.Collections.Generic;

namespace BinaryDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //方法一
            /*
            BinaryTree binarytree = new BinaryTree();
            //在代码中手动的创建了二叉树
            binarytree.CreateBinaryTree();
            //先序遍历
            binarytree.PreOrder(binarytree.root);
            Console.WriteLine();
            //中序遍历
            binarytree.MidOrder(binarytree.root);
            Console.WriteLine();
            //后序遍历
            binarytree.LastOrder(binarytree.root);
            */
            
            //方法二
            
            //用集合存储所有的结点
            List<String> data = new List<string>();
            //存储先序遍历每一个结点的数组
            String[] dataArray = new string[] {"A","B","D","#","#","E","#","#","C","#","F","#","#"};
            //遍历存储结点的数组存储到集合里面
            foreach (string item in dataArray)
            {
                data.Add(item);
            }
            BinaryTree binary = new BinaryTree();
            binary.CreateBinaryTree(data);//创建二叉树

            int height = binary.GetHeight();//求二叉树的高度
            Console.WriteLine("二叉树的高度是"+height);

            int size = binary.GetSize();//过去所以的结点数
            Console.WriteLine("二叉树的结点数是"+size);
            binary.TheFirstOrder(binary.root);
            Console.WriteLine();
            binary.TheMidleOrder(binary.root);
            Console.WriteLine();
            binary.TheLastOrder(binary.root);
            
            Console.ReadKey();
        }
    }
}