1. Data Structures and Database Applications Linked Lists

2. LinkedList System.Collections.Generic.LinkedList
Automatic resizing and homogeneous list
Represents a doubly linked list of nodes

3. Object References
Recall that an object reference is a variable that stores the address of an object
A reference also can be called a pointer
References often are depicted graphically:
student
John Smith
40725
3.58

4. References as Links
Object references can be used to create links between objects
Suppose a class contains a reference to another object of the same class:
class Node {
Object info;
Node next; }

5. References as Links
References can be used to create a variety of linked structures, such as a linked list:

6. Using Intermediate Nodes
The objects being stored should not be concerned with the details of the data structure in which they may be stored
For example, a list of students created with a Student class should not have to store a link to the next Student object in the previous Student object
Instead, a separate node class is used in the LinkedList class which serves two functions:
It has a reference to the data object (e.g the Student object)
It has a link to the next (and possibly previous) nodes in the list
The internal representation becomes a linked list of nodes

7. Inserting a Node
Internally, a node is inserted into a linked list with a few reference changes:

8. Deleting a Node
Likewise, a node is removed from a linked list by changing the next pointer of the preceding node:

9. Other Dynamic Representations
When a linked list structure has both next and previous references, it is a doubly linked list:
class Node {
Object info;
Node next;
Node prev; }

10. LinkedList
Example:
LinkedList<string> sentence = new LinkedList<string>(); // instantiates ls object
sentence.AddFirst("fox"); // add "fox" as first item
sentence.AddLast("jumped"); // add “jumped" as last item
sentence.AddLast("dog"); // add “dog" as new last item
sentence.AddBefore(sentence.Last, "the"); // add “the” before “dog”
LinkedListNode<string> current = sentence.First;
while (current.Next != null) // loop through all values {
Console.Write(current.Value + " ");
current = current.Next;
} // prints: fox jumped the dog
Console.WriteLine();

11. LinkedList Example (continued):
sentence.AddAfter(sentence.First.Next, "over"); // add "over" after "jumped"
sentence.AddFirst("the"); // add "the" as first word
LinkedListNode<string> current = sentence.First;
while (current.Next != null) {
Console.Write(current.Value + " ");
current = current.Next;
} // now prints: the fox jumped over the dog
Console.WriteLine();
Console.ReadLine();

12. Other Dynamic Representations
Internally, a linked list can also use a separate header node, which can store the amount of nodes (count) and references to both the front and rear of the list:

13. Common LinkedList Methods
AddAfter()
AddBefore()
AddFirst()
AddLast()
Remove()
RemoveFirst()
RemoveLast()
Clear()
Contains()
Find()
FindLast()