二叉查找树

    using System;

    public class BinarySearchTree
    {
        public int value;

        public BinarySearchTree left = null;
        public BinarySearchTree right = null;
        public BinarySearchTree parent = null;
        public BinarySearchTree root = null;

        private bool _isRoot;
        public bool isRoot
        {
            get { return _isRoot; }
            set
            {
                _isRoot = value;
                root = _isRoot ? this : null;
            }
        }

        public BinarySearchTree(int value,BinarySearchTree parent,BinarySearchTree root)
        {
            this.value = value;
            this.parent = parent;
            this.root = root;
        }
        public BinarySearchTree(int value) : this(value, null, null) { }

        /// <summary>
        /// 增
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public void InsertNode(int value)
        {
            if(value <= this.value)
            {
                if(left == null)
                {
                    left = new BinarySearchTree(value,this,root);
                    return;
                }
                else if(left != null)
                {
                    left.InsertNode(value);
                    return;
                }
            }
            else if(value > this.value)
            {
                if(right == null)
                {
                    right = new BinarySearchTree(value,this,root);
                    return;
                }
                else if(right != null)
                {
                    right.InsertNode(value);
                    return;
                }
            }
        }

        /// <summary>
        /// 删
        /// </summary>
        /// <param name="value"></param>
        /// <exception cref="Exception"/>
        public void RemoveNode(int value)
        {
            BinarySearchTree beRemove = null;
            try
            {
                beRemove = Find(value);
            }
            catch (Exception)
            {
                throw new Exception("被删除的数字不存在");
            }

            if (beRemove.left == null && beRemove.right == null)
            {
                if (beRemove.parent.left == beRemove)
                {
                    beRemove.parent.left = null;
                }
                else if (beRemove.parent.right == beRemove)
                {
                    beRemove.parent.right = null;
                }
            }
            else if(beRemove.left != null && beRemove.right == null)
            {
                if (beRemove.parent.left == beRemove)
                {
                    beRemove.parent.left = beRemove.left;
                }
                else if (beRemove.parent.right == beRemove)
                {
                    beRemove.parent.right = beRemove.left;
                }
            }
            else if(beRemove.left == null && beRemove.right != null)
            {
                if (beRemove.parent.left == beRemove)
                {
                    beRemove.parent.left = beRemove.right;
                }
                else if (beRemove.parent.right == beRemove)
                {
                    beRemove.parent.right = beRemove.right;
                }
            }
            else if(beRemove.left != null && beRemove.right != null)
            {
                if (beRemove.parent.left == beRemove)
                {
                    beRemove.parent.left = beRemove.right;
                }
                else if (beRemove.parent.right == beRemove)
                {
                    beRemove.parent.right = beRemove.right;
                }

                beRemove.right.left = beRemove.left;
            }
        }

        /// <summary>
        /// 改
        /// </summary>
        /// <param name="newValue"></param>
        public void ChangeNoodTo(int newValue)
        {
            RemoveNode(value);
            root.InsertNode(newValue);
        }

        /// <summary>
        /// 查
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        /// <exception cref="Exception"/>
        public BinarySearchTree Find(int value)
        {
            if (value < this.value)
            {
                //return left == null ? -1 : left.Find(value);
                if(left == null)
                {
                    throw new Exception("被搜索的数字不存在");
                }
                else
                {
                    return left.Find(value);
                }
            }
            else if (value > this.value)
            {
                //return right == null ? -1 : right.Find(value);
                if(right == null)
                {
                    throw new Exception("被搜索的数字不存在");
                }
                else
                {
                    return right.Find(value);
                }
            }
            else if (value == this.value)
            {
                return this;
            }

            throw new Exception("被搜索的数字不存在");
        }
        
        /// <summary>
        /// 输出这棵二叉搜索树
        /// </summary>
        public void ShowTree()
        {
            Console.Write("(");
            Console.Write(this.value);
            if(left == null)
            {
                Console.Write("()");
            }
            else
            {
                left.ShowTree();
            }

            if(right == null)
            {
                Console.Write("()");
            }
            else
            {
                right.ShowTree();
            }

            Console.Write(")");
        }

        /// <summary>
        /// 复写 ToString() 方法
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            return value.ToString();
        }
    }

    class Program
    {

        private static int[] value = new int[] { 50, 60, 70, 23, 51, 159, 25 };

        static void Main(string[] args)
        {
            BinarySearchTree rootNood = new BinarySearchTree(value[0]);
            rootNood.isRoot = true;

            Console.WriteLine(rootNood.root == null);

            for (int i = 1; i < value.Length; i++)
            {
                rootNood.InsertNode(value[i]);
            }

            rootNood.ShowTree();
            Console.WriteLine();
            
            rootNood.Find(23).ChangeNoodTo(24);
            rootNood.ShowTree();
            

            Console.ReadKey();
        }
    }