namespace InterviewImproveCode

{

    using System;

    using System.Collections.Generic;

    using System.Collections.ObjectModel;

    using System.Linq;

    internal class Program

    {

        public static void Main(string[] args)

        {

​

            TreeNode<string> treeNode = new TreeNode<string>("Root");

            treeNode.AddChild("child1").AddChild("child1_grandchild1").AddChild("child1_grandchild2");

            treeNode.AddChild("child2").AddChild("child2_grandchild1");

​

            Console.WriteLine(string.Join(",", treeNode.Flatten()));

            var grandchild_changedName = treeNode.Find("child2_grandchild1");

            grandchild_changedName.Value = "child2_grandchild_1";

​

            Console.WriteLine(string.Join(",", treeNode.Flatten()));

        }

    }

    public class TreeNode<T>

    {

        private T _value;

        private readonly List<TreeNode<T>> _children = new List<TreeNode<T>>();

​

        public TreeNode(T value)

        {

            _value = value;

        }

​

        public TreeNode<T> this[int i]

        {

            get { return _children[i]; }

        }

​

        public TreeNode<T> Parent { get; private set; }

​

        public T Value

        {

            get

            {

                return _value;

            }

            set { _value = value; }

        }

​

        public ReadOnlyCollection<TreeNode<T>> Children

        {

            get { return _children.AsReadOnly(); }

        }

​

        public TreeNode<T> AddChild(T value)

        {

            var node = new TreeNode<T>(value) { Parent = this };

            _children.Add(node);

            return node;

        }

​

        public TreeNode<T>[] AddChildren(params T[] values)

        {

            return values.Select(AddChild).ToArray();

        }

​

        public bool RemoveChild(TreeNode<T> node)

        {

            return _children.Remove(node);

        }

​

        public void Traverse(Action<T> action)

        {

            action(Value);

            foreach (var child in _children)

                child.Traverse(action);

        }

        public TreeNode<T> Find(T value)

        {

            TreeNode<T> treeNode = null;

            Find(this, value, ref treeNode);

            return treeNode;

        }

​

        private void Find(TreeNode<T> treeNode, T Value, ref TreeNode<T> temp)

        {

            if (treeNode != null && temp == null)

            {

                if (treeNode.Value == (dynamic)Value)

                    temp = treeNode;

                else

                {

                    while (treeNode.Children.Count > 0)

                    {

                        foreach (var child in treeNode.Children)

                        {

                            Find(child, Value, ref temp);

                        }

                    }

                }

            }

        }

​

        public IEnumerable<T> Flatten()

        {

            return new[] { Value }.Concat(_children.SelectMany(x => x.Flatten()));

        }

    }

}

​

​