delegate void TreeVisitor<T>(T nodeData);

class NTree<T>

{

    private T data;

    private LinkedList<NTree<T>> children;

    public NTree(T data)

    {

         this.data = data;

        children = new LinkedList<NTree<T>>();

    }

    public void AddChild(T data)

    {

        children.AddFirst(new NTree<T>(data));

    }

    public NTree<T> GetChild(int i)

    {

        foreach (NTree<T> n in children)

            if (--i == 0)

                return n;

        return null;

    }

    public void Traverse(NTree<T> node, TreeVisitor<T> visitor)

    {

        visitor(node.data);

        foreach (NTree<T> kid in node.children)

            Traverse(kid, visitor);

    }

}

namespace Overby.Collections

{

    public class TreeNode<T>

    {

        private readonly 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; } }

        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 IEnumerable<T> Flatten()

        {

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

        }

    }

}