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

namespace DoubleLinkedList
{
    class Program
    {
        static void Main(string[] args)
        {
            DoubleLinkedList myList = new DoubleLinkedList();

            myList.AddLast(2);
            myList.AddFirst(1);
            myList.AddFirst(0);

            myList[2] = 3;
            myList.Remove(3);
            DoubleLinkedList myList2 = new DoubleLinkedList(myList);
            Console.WriteLine(myList[1]);
            Console.ReadKey();
        }
    }
    class DoubleLinkedList
    {
        ListElement first = null;
        ListElement last = null;
        int count = 0;

        public int Count => count;

        public DoubleLinkedList()
        {
            first = last = null;
        }
        public DoubleLinkedList(DoubleLinkedList list)
        {
            ListElement tempCopy = list.first;
            while (tempCopy != null)
            {
                this.AddLast(tempCopy.value);
                if (tempCopy.next != null)
                    tempCopy = tempCopy.next;
                else
                    tempCopy = null;
            }
        }
        public int this[int index]
        {
            get
            {
                if (index < 0 || index >= count) throw new IndexOutOfRangeException();
                ListElement temp = first;
                int i = index;
                while(i-- > 0)
                    temp = temp.next;
                return temp.value;
            }
            set
            {
                if (index < 0 || index >= count) throw new IndexOutOfRangeException();
                ListElement temp = first;
                int i = index;
                while (i-- > 0)
                    temp = temp.next;
                temp.value = value;
            }
        }

        public void AddFirst(int value)
        {
            ListElement newElement = new ListElement(value);
            if (count == 0)
            {
                first = newElement;
                last = newElement;
            }
            else
            {
                newElement.next = first;
                first.prev = newElement;
                first = newElement;
            }
            count++;
        }
        public void AddLast(int value)
        {
            ListElement newElement = new ListElement(value);
            if (count == 0)
            {
                first = newElement;
                last = newElement;
            }
            else
            {
                newElement.prev = last;
                last.next = newElement;
                last = newElement;
            }
            count++;
        }

        public void Remove(int value)
        {
            if (count <= 0) throw new Exception("List is empty!");
            ListElement temp = first;
            for(int i = 0; i < count; i++)
            {
                if(temp.value == value)
                {
                    if (i == 0)
                        first = first.next;
                    if (i == count - 1)
                        last = last.prev;
                    if (temp.next != null)
                    {
                        temp.next.prev = temp.prev;
                        temp.prev.next = temp.next;
                    }
                    else
                        temp.prev.next = null;
                    temp = null;
                    count--;
                    return;
                }
                temp = temp.next;
            }
        }

        private class ListElement
        {
            public int value;
            public ListElement next = null;
            public ListElement prev = null;
            public ListElement(int Value, ListElement Next = null, ListElement Prev = null)
            {
                value = Value;
                next = Next;
                prev = Prev;
            }
        }
    }
}