1. Data Structures & Algorithms
CHAPTER 5
Linked List
Ms. Manal Al-Asmari

2. Motivation Suppose I have an array: 1,4,10,19,6
I want to insert a 7 between the 4 and the 10
What do I need to do?
What about deleting an element from the array ?
Ms. Manal Al-Asmari

3. Need for Linked list
We need an alternative structure that stores elements in a
sequence but allows for more efficient insertion and deletion of
elements at random positions in the list.
In a linked list, elements contain links that reference the successor
element in the list.
Inserting and deleting an element is a local operation and requires
updating only the links adjacent to the element. The other
elements in the list are not affected.
An Array must shift all elements on the tail whenever a new
element enters or exits the list.
Ms. Manal Al-Asmari

4. Arrays vs. Linked lists Arrays have a pre-determined fixed size
easy access to any element a[i] in constant time
no space overhead
S = n x sizeof(element)
Linked lists
no fixed size; grow one element at a time
space overhead
each element must store an additional reference
S = n x sizeof (element) + n x sizeof(reference)
no easy access to i-th element
need to hop through all previous elements
Ms. Manal Al-Asmari

5. Linked Lists “Reference-Based Lists”
List of items, called nodes
The order of the nodes is determined by the address, called the link, stored in each node.
Every node (except the last node) contains the address of the next node
Components of a node
Data: stores the relevant information
Link: stores the address of the next node
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6. Structure of Linked Lists
Figure1: Structure of a node
Figure2: Linked list
Head or first
holds the address of the first node in the list
The info part of the node
can be either a value of a primitive type or a reference to an object
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7. Linked Lists Class Node Represents nodes on a list
It has two instance variables
* info (of type int, but it can be any other type)
* link (of type Node)
public class Node {
public int info;
public Node link; }
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8. Linked List: Some properties
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9. Linked List: Some properties
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10. Linked List: Some properties
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11. Linked List: Some properties
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12. Traversing a Linked List
Basic operations of a linked list that require the link to be traversed:
* Search the list for an item
* Insert an item in the list
* Delete an item from the list
You cannot use head to traverse the list
* You would lose the nodes of the list
*Use another reference variable of the same type as
head: current
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13. Traversing a Linked List
The following code traverses the list
current = head;
while (current != null) {
//Process current
current = current.link; }
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14. Insertion
Consider the following linked list
You want to create a new node with info 50 and insert it after p
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15. Insertion
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16. Insertion
The following statements insert the node in the linked list at the required place
newNode.link = p.link;
p.link = newNode;
The sequence of statements to insert the node is very important
Ms. Manal Al-Asmari

17. Insertion
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18. Deletion
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19. Building a Linked List You can build a list in two ways:
forward or backward:
Forward manner
A new node is always inserted at the end of the linked list
Backward manner
A new node is always inserted at the beginning of the linked list
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20. Types of Linked Lists: Doubly Linked Lists Circular Linked Lists
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21. 1\ Doubly Linked Lists
Linked list in which every node has a next link and a back link.
A doubly linked list can be traversed in either direction
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22. 2\ Circular Linked Lists
A linked list in which the last node refers to the first node.
It is convenient to make first point to the last node.
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23. THE END
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