using System;

namespace MyList
{
    public class Node<T>
    {
        public Node<T> Next { get; set; }
        public T Value { get; set; }

        public Node(T value)
        {
            Value = value;
        }
    }
    public class MyList<T>
    {
        private const string MsgError =
            "Index was out of range. Must be non-negative and less than the size of the collection. ";

        private Node<T> _head;
        private int _count;

        public int Count
        {
            get => _count;
        }

        public T this[int index]
        {
            get
            {
                if (index >= Count || index < 0)
                    throw new ArgumentOutOfRangeException(
                        MsgError);

                Node<T> ret = _head;
                for (int i = 0; i < index; i++)
                {
                    ret = ret.Next;
                }

                return ret.Value;
            }
            set
            {
                if (index >= Count || index < 0)
                    throw new ArgumentOutOfRangeException(
                        MsgError);

                Node<T> ret = _head;
                for (int i = 0; i < index; i++)
                {
                    ret = ret.Next;
                }

                ret.Value = value;
            }
        }

        public void Clear()
        {
            _head = null;
            _count = 0;
        }


        public void RemoveAt(int index)
        {
            if (index >= _count || index < 0)
                throw new ArgumentOutOfRangeException(
                    MsgError);

            if (index == 0)
            {
                _head = _head.Next;
            }
            else
            {
                Node<T> node = _head;

                for (int i = 0; i < index - 1; i++)
                {
                    node = node.Next;
                }

                node.Next = node.Next?.Next;
            }

            _count--;
        }

        public void Add(T value)
        {
            if (_head == null)
            {
                _head = new Node<T>(value);
            }
            else
            {
                Node<T> temp = _head;
                while (temp.Next != null)
                {
                    temp = temp.Next;
                }

                temp.Next = new Node<T>(value);
            }

            _count++;
        }
    }
}