C#数据结构之Tree

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AlgorithmsDemo
{
    public class TreeNode<T>
    {
        public T Data { get; set; }
        public List<TreeNode<T>> Children { get; set; } 
        
    }
    public class Tree<T>
    {
        public TreeNode<T> Root { get; set; }
    }

    //
    public class BinaryTreeNode<T> : TreeNode<T>
    {
        public BinaryTreeNode()
        {
            Children = new List<TreeNode<T>>() { null, null };
        }
        public  BinaryTreeNode<T> Parent { get; set; }

        public BinaryTreeNode<T> Left
        {
            get
            {
                return (BinaryTreeNode<T>)Children[0];
            }
            set
            {
                Children[0] = value;
            }
        }
        public BinaryTreeNode<T> Right
        {
            get
            {
                return (BinaryTreeNode<T>)Children[1];
            }
            set
            {
                Children[1] = value;
            }
        }
        public int GetHeight()
        {
            int height = 1;
            BinaryTreeNode<T> current = this;
            while (current.Parent != null)
            {
                height++;
                current = current.Parent;
            }
            return height;
        }
    }
    /// <summary>
    /// 二叉树遍历类型
    /// </summary>
    public enum TranversalEnum
    {
        PREORDER,
        INORDER,
        POSTORDER,
    }

    public class BinaryTree<T>
    {
        public BinaryTreeNode<T> Root { get; set; }
        /// <summary>
        /// 二叉树所有节点数量
        /// </summary>
        public int Count { get; set; }

        private void TranversePreOrder(BinaryTreeNode<T> node,List<BinaryTreeNode<T>> result)
        {
            if(node != null)
            {
                result.Add(node);//前序遍历
                TranversePreOrder(node.Left, result);
                TranversePreOrder(node.Right, result);
            }
        }
        private void TranverseInOrder(BinaryTreeNode<T> node,List<BinaryTreeNode<T>> result)
        {
            if(node != null)
            {
                TranverseInOrder(node.Left, result);
                result.Add(node);
                TranverseInOrder(node.Right, result);
            }
        }
        private void TranversePostOrder(BinaryTreeNode<T>node,List<BinaryTreeNode<T>> result)
        {
            if(node != null)
            {
                TranversePostOrder(node.Left,result);
                TranversePostOrder(node.Right, result);
                result.Add(node);
            }
        }
        /// <summary>
        /// 遍历
        /// </summary>
        /// <param name="mode"></param>
        /// <returns></returns>
        public List<BinaryTreeNode<T>> Tranverse(TranversalEnum mode)
        {
            List<BinaryTreeNode<T>> nodes = new List<BinaryTreeNode<T>>();
            switch (mode)
            {
                case TranversalEnum.PREORDER:
                    TranversePreOrder(Root, nodes);
                    break;
                case TranversalEnum.INORDER:
                    TranverseInOrder(Root, nodes);
                    break;
                case TranversalEnum.POSTORDER:
                    TranversePostOrder(Root, nodes);
                    break;
            }
            return nodes;
        }
        public int GetHeight()
        {
            int height = 0;
            foreach(var node in Tranverse(TranversalEnum.PREORDER))
            {
                height = Math.Max(height, node.GetHeight());
            }
            return height;
        }

    }

    public class BinarySearchTree<T> : BinaryTree<T> where T:IComparable
    {
        public bool Contains(T data)
        {
            BinaryTreeNode<T> node = Root;
            while(node != null)
            {
                int result = data.CompareTo(node.Data);
                if (result == 0)
                {
                    return true;
                }
                else if (result < 0)
                {
                    node = node.Left;
                }
                else
                {
                    node = node.Right;
                }
            }
            return false;
        }
        private BinaryTreeNode<T> GetParentForNewNode(T data)
        {
            BinaryTreeNode<T> current = Root;
            BinaryTreeNode<T> parent = null;
            while(current != null)
            {
                parent = current;
                int result = data.CompareTo(current.Data);
                if (result == 0)
                {
                    throw new ArgumentException($"The node {data} already exists");
                }
                else if (result < 0)
                {
                    current = current.Left;
                }
                else
                {
                    current = current.Right;
                }
            }

            return parent;
        }
        public void Add(T data)
        {
            BinaryTreeNode<T> parent=GetParentForNewNode(data);
            BinaryTreeNode<T> node = new BinaryTreeNode<T>() { Data=data,Parent=parent};
            if (parent == null)
            {
                Root = node;
            }
            else if (data.CompareTo(parent.Data) < 0)
            {
                parent.Left = node;
            }
            else
            {
                parent.Right = node;
            }
            Count++;
        }
        public void Remove(T data)
        {

        }
        /// <summary>
        /// 从以根节点未node的树中，移除含有data的节点
        /// </summary>
        /// <param name="node"></param>
        /// <param name="data"></param>
        /// <exception cref="ArgumentException"></exception>
        private void Remove(BinaryTreeNode<T> node,T data)
        {
            if (node == null)
            {
                throw new ArgumentException($"The node {data} does not exist");
            }
            else if (data.CompareTo(node.Data) < 0)
            {
                Remove(node.Left, data);
            }
            else if (data.CompareTo(node.Data) > 0)
            {
                Remove(node.Right, data);
            }
            else //移除的节点找到了
            {
                if(node.Left==null && node.Right == null)
                {
                    //是叶节点，将该节点替换为null
                    ReplaceInParent(node, null);
                    Count--;
                }
                else if (node.Right == null)
                {
                    //右节点为空,用该节点的左节点替换该节点
                    ReplaceInParent(node,node.Left);
                    Count--;
                }
                else if (node.Left == null)
                {
                    //左节点为空，用改节点的右节点替换该节点
                    ReplaceInParent(node, node.Right);
                    Count--;

                }
                else
                {
                    //左右节点都不为空,找到以该节点的右节点为根节点的子树的最小节点，
                    //将上述最小节点的值替换到该节点的值，然后再移除最小节点上的数据。
                    BinaryTreeNode<T> succor = FindMininumInSubTree(node.Right);
                    //succor的左节点一定是null，后续Remove方法，一定进入左节点是空的分支。
                    node.Data=succor.Data;
                    Remove(succor, succor.Data);//
                }
            }
        }
        /// <summary>
        /// 替换节点，删除node，用newNode来替换node
        /// </summary>
        /// <param name="node"></param>
        /// <param name="newNode"></param>
        private void ReplaceInParent(BinaryTreeNode<T> node,BinaryTreeNode<T> newNode)
        {
            //首先变更node.Parent中含有的对node的信息
            if (node.Parent != null)
            {
                if (node.Parent.Left == node)
                {
                    node.Parent.Left = newNode;
                }
                else
                {
                    node.Parent.Right = newNode;
                }
            }
            else
            {
                Root = newNode;
            }
            //再变更newNode中有关Parent的信息
            if(newNode != null)
            {
                newNode.Parent = node.Parent;
            }
        }
        /// <summary>
        /// 找到以node为根节点的子树的最小节点
        /// </summary>
        /// <param name="node"></param>
        /// <returns></returns>
        private BinaryTreeNode<T> FindMininumInSubTree(BinaryTreeNode<T> node)
        {
            while(node.Left != null)
            {
                node= node.Left;
            }
            return node;
        }

    }
    

}