Linked Lists

Here is another example of a linked list. This time, the list allows you to add an item to the beginning or the end of the list:

using System;

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

public class LinkedList<T>
{
    private  Node<T> begin;
    private  Node<T> end;
    private int size;

    public LinkedList()
    {
        begin = null;
        end = null;
        size = 0;
    }

    public int Count
    {
        get { return size; }
    }

    public void AddFirst(Node<T> item)
    {
        // Get a reference to the node we want to add
        Node<T> current = item;

        // If the list is currently empty, specify that the first
        // and the last are the same and they will receive the argument
        if (begin == null)
            begin = end = current;
        else // If there is already at least one item in the collection
        {
            // Get a reference to the current first item
            Node<T> first = this[0];
            // Get the next item to the first and assign it
            // to the next item of the argument
            current.Next = first.Next;
            // Replace the next item of the first with the argument
            first.Next = current;
        }

        // Increase the count of items
        size++;
    }

    public void AddLast(Node<T> item)
    {
        // Get a reference to the new item that will be added
        // and assign the argument to that reference
        Node<T> current = item;

        // Indicate that the first node will become next to the new item
        current.Next = begin;
        // Indicate that the new item becomes the first of the collection
        begin = current;

        // Increase the count of items
        size++;
    }

    public void Delete()
    {
        if (begin == null)
            return; // throw new NullReferenceException("The list is currently empty");

        Node<T> current;

        current = begin.Next;
        begin.Next = current.Next;
        size--;
    }

    public void Clear()
    {
        size = 0;
    }

    public void Show()
    {
        Console.Write("Current List: ");
        for (Node<T> current = begin; current != null; current = current.Next)
            Console.Write(current.Value + " - ");
        Console.WriteLine();
    }

    public Node<T> Get(int index)
    {
        Node<T> current = begin;

        for (int i = size - 1; (i > index) && (current != null); i--)
            current = current.Next;
        return current;
    }

    public Node<T> this[int index]
    {
        get
        {
            Node<T> current = begin;

            for (int i = size - 1; (i > index) && (current != null); i--)
                current = current.Next;
            return current;
        }
    }

    public override string ToString()
    {
        string result = "- ";
        Node<T> current = begin;

        if (begin == null) // throw new NullReferenceException("The list is currently empty");
            return "The list is currently empty";
        else
        {
            for (int i = 0; i < size; i++)
            {
                result = result + current.Value + " - ";
                current = current.Next;
            }
        }

        return result;
    }
}

public class Exercise
{
    static int Main(string[] args)
    {
        Node<string> name = null;
        LinkedList<string> employees = new LinkedList<string>();

        name = new Node<string>();
        name.Value = "Alan Baxter";
        employees.AddFirst(name);

        name = new Node<string>();
        name.Value = "Joan Bramble";
        employees.AddLast(name);

        name = new Node<string>();
        name.Value = "Lionel Berg";
        employees.AddLast(name);

        name = new Node<string>();
        name.Value = "Paul Bertrand Yamaguchi";
        employees.AddFirst(name);

        name = new Node<string>();
        name.Value = "Flora Bruze";
        employees.AddLast(name);

        name = new Node<string>();
        name.Value = "Christopher Fox";
        employees.AddLast(name);

        name = new Node<string>();
        name.Value = "Holly Madsen";
        employees.AddFirst(name);

        for(int i = 0; i < employees.Count; i++)
            Console.WriteLine("Name {0}: {1}", i + 1, employees[i].Value);

        Console.WriteLine("----------------------------------");

        employees.Delete();

        for (int i = 0; i < employees.Count; i++)
            Console.WriteLine("Name {0}: {1}", i + 1, employees[i].Value);

        return 0;
    }
}

This would produce:

Name 1: Holly Madsen
Name 2: Paul Bertrand Yamaguchi
Name 3: Alan Baxter
Name 4: Joan Bramble
Name 5: Lionel Berg
Name 6: Flora Bruze
Name 7: Christopher Fox
----------------------------------
Name 1: Holly Madsen
Name 2: Paul Bertrand Yamaguchi
Name 3: Alan Baxter
Name 4: Joan Bramble
Name 5: Lionel Berg
Name 6: Christopher Fox
Press any key to continue . . .