Introduction to Linked List

Summary

This presentation introduces linked lists as a data structure for arranging elements like student names alphabetically. It contrasts linked lists with arrays, highlighting linked lists' ability to overcome arrays' limitations. The video explains different types of linked lists: single, doubly, and circular. It details how a single linked list is composed of nodes with data and a link to the next node, allowing forward navigation only. The script concludes by discussing how to access and traverse a linked list using a 'head' pointer.

Takeaways

• 📚 The presentation introduces linked lists as a new data structure for arranging data, specifically student names by the first letter.
• 🔍 The goal is to maintain a list in memory, with linked lists being one of the two methods (the other being arrays).
• 🚫 Arrays have limitations and disadvantages, which linked lists aim to overcome.
• 🔑 Linked lists come in different types: singly linked, doubly linked, and circular linked lists.
• ➡️ In a singly linked list, navigation is forward-only, making it the most basic type of linked list.
• 🔄 A doubly linked list allows for both forward and backward navigation.
• 🔁 Circular linked lists have their last element linked to the first, creating a loop.
• 💡 A node in a linked list consists of two parts: data and a link to the next node.
• 📝 Nodes in a linked list do not need to be stored in sequential order in memory, unlike arrays.
• 🔗 The link part of each node contains the address of the next node, enabling traversal of the list.
• 👉 A pointer named 'head' is used to access the first node of the linked list, making the entire list accessible.

Q & A

What is the main topic of this presentation?

The main topic of this presentation is linked lists, specifically introducing what a linked list is and how it looks like.

What is the purpose of arranging student names in the presentation?

The purpose of arranging student names is to demonstrate how to maintain a list in memory, specifically in sequential order according to the first letter of their names.

What are the two ways mentioned to maintain a list in memory?

The two ways to maintain a list in memory are using an array data structure and using a linked list data structure.

What is a single linked list?

A single linked list is a list made up of nodes where each node contains data and a link to the next node in the list, allowing forward-only navigation.

How does a doubly linked list differ from a single linked list?

A doubly linked list differs from a single linked list in that it allows forward and backward navigation due to each node containing a link to both the next and previous nodes.

What is a circular linked list?

A circular linked list is a type of linked list where the last element is linked back to the first element, creating a circular structure.

What are the two main parts of a node in a single linked list?

The two main parts of a node in a single linked list are the data part, which contains the actual data, and the link part, which contains the address of the next node in the list.

Why don't nodes in a linked list need to be stored in sequential order in memory?

Nodes in a linked list do not need to be stored in sequential order in memory because the list's structure is defined by the links between nodes, not by their physical memory addresses.

What does the NULL value in the last node of a linked list signify?

The NULL value in the last node of a linked list signifies that it is the end of the list, indicating that there are no more nodes to follow.

How is the first node of a linked list accessed?

The first node of a linked list is accessed using a pointer, typically named 'head', which contains the address of the first node.

What is the next step after understanding how a single linked list looks like?

The next step after understanding how a single linked list looks like is to learn how to create a single linked list programmatically and perform different operations on it.

Outlines

00:00

🔗 Introduction to Linked Lists

The script introduces the concept of linked lists as a data structure used to maintain a list in memory. It contrasts linked lists with arrays and highlights their ability to overcome the limitations of arrays. The presenter explains the different types of linked lists: single, doubly, and circular. The focus is on single linked lists, which allow forward navigation only. A node in a single linked list consists of two parts: data and a link to the next node. An example is given where nodes containing student names are arranged alphabetically, and their addresses in memory are discussed to illustrate how linked lists are not stored in sequential memory locations like arrays.

05:00

👤 Accessing Nodes in a Linked List

This section explains how to access nodes in a linked list. It emphasizes the importance of having the address of the first node to access the entire list. A pointer named 'head' is introduced to access the first node, which is crucial for traversing the list. The script concludes by mentioning that future lectures will cover how to create and manipulate linked lists programmatically, similar to array operations.

Keywords

💡Linked List

A linked list is a linear data structure in which elements are stored in nodes, and each node points to the next node in the sequence. It is a fundamental concept in data structures used for organizing and storing collections of data. In the video, linked lists are introduced as a way to maintain a list in memory, contrasting with arrays, and are the central theme of the presentation.

💡Node

A node is a fundamental building block of a linked list, typically consisting of data and a reference (or link) to the next node in the sequence. Nodes are the units that make up a linked list, and understanding their structure is crucial for grasping how linked lists function. In the script, nodes are described as containing both data (like student names or numbers) and links to the next node.

💡Array

An array is a data structure consisting of a collection of elements, each identified by one or more indices or keys. It is presented in the video as an alternative to linked lists for maintaining a list in memory, with certain limitations and disadvantages that linked lists aim to overcome.

💡Data Structure

A data structure is a specialized format for organizing, processing, retrieving, and storing data. The video discusses arrays and linked lists as two types of data structures, emphasizing their roles in managing data in computer memory.

💡Single Linked List

A single linked list is a type of linked list in which each node is linked to the next node in the sequence, allowing traversal in only one direction: forward. The video explains that in a single linked list, navigation is forward-only, which is a defining characteristic.

💡Doubly Linked List

A doubly linked list is a variation of the linked list in which each node contains a pointer to both the next node and the previous node, allowing traversal in both directions: forward and backward. This is contrasted with a single linked list in the script, where only forward navigation is possible.

💡Circular Linked List

A circular linked list is a type of linked list where the last node in the sequence points back to the first node, forming a circle. This concept is introduced in the video to illustrate another variation of linked lists, where the ending node does not point to null but rather to the head of the list.

💡Memory

Memory, in the context of the video, refers to the computer's storage used to hold data. The video discusses how different data structures, like arrays and linked lists, are used to maintain lists in memory, emphasizing the importance of efficient memory usage.

💡Pointer

A pointer is a variable that stores the memory address of another variable. In the context of linked lists, pointers are used to reference the memory address of the next node in the sequence. The video mentions that a pointer named 'head' is used to access the first node of a linked list.

💡Sequential Order

Sequential order refers to the arrangement of elements in a specific order, such as alphabetical or numerical. The video uses the example of arranging student names according to the first letter to illustrate the concept of sequential order and how linked lists can be used to maintain such an order.

💡Disadvantages

Disadvantages, in the context of the video, refer to the limitations or negative aspects of a particular data structure. The script mentions that arrays have certain disadvantages, which are then contrasted with the benefits of linked lists, setting the stage for a comparative analysis in subsequent lectures.

Highlights

Introduction to linked lists and their purpose.

Objective to arrange student names alphabetically using linked lists.

Explanation of how to maintain a list in memory using data structures.

Comparison between array and linked list data structures.

Advantages of linked lists over arrays.

Types of linked lists: single, doubly, and circular.

Definition and characteristics of a single linked list.

Explanation of node structure in a linked list.

How nodes are not stored sequentially in memory in a linked list.

Process of creating a single linked list with example numbers.

Illustration of how to link nodes to form a list.

The significance of the 'NULL' value in the last node's link.

How to access the first node of a linked list using a pointer.

Naming convention for the pointer to the first node (head).

Accessing the entire list through the head pointer.

Upcoming topics on creating and operating linked lists programmatically.

Conclusion and thanks for watching the presentation.

Transcripts

From this presentation onwards,

we are starting with the new chapter called linked list

and in this particular presentation, I will introduce

what a linked list is all about and how it looks like.

So let's get started.

Let's say our target is to arrange the name of the students

according to the first letter of their names.

This is our target.

We need to arrange the name of the students.

These are the names available with us.

We need to arrange them in sequential order

that too according to the first letter of their names.

And this is how the order looks like, right?

Of course, the first name must be Alpha.

Then we have John, then Mark, Michael, Rock, Smith, Tony.

These are the names arranged in a sequential order

according to the first letter of the names.

Now my question is, how to maintain this list in a memory?

That is, the actual memory.

In order to maintain a list in a memory,

there are basically two ways available with us.

The first one is of course, by using array data structure.

The other one is using linked list data structure.

By using these two ways,

we can maintain a list in a memory.

These are basically the data structures.

We have already dealt with array data structure.

Now, in this presentation and in the subsequent presentation,

we will deal with how to maintain

a list using linked list.

Arrays have some limitations and disadvantages

and there is no doubt about it.

This is very sad.

But we will see, how linked list overcomes

the limitations and disadvantages of arrays.

We will see, what are the disadvantages

and limitations of arrays and we will see

how linked list overcome those limitations and disadvantages

in the subsequent lectures.

But for now, we will see

what are the different types of linked list we are available with.

The first one is of course, single linked list.

This is the basic type

and the first type of linked list.

Basically, in single linked list navigation is forward only.

That means we can go in forward direction

and we can't go backwards.

So navigation is forward only.

This is the way, we can identify a linked list is a single linked list.

When the navigation is forward only,

then it is called as a single linked list.

But when the navigation is forward and backward,

then it is called a doubly linked list.

So here, in the doubly linked list

forward and backward navigation is possible.

We have another type called circular linked list.

Here, the last element is linked to the first element

as the name itself suggests, that is a circular linked list.

So definitely the last element must be linked to the first element.

Now, we will discuss what is a single linked list.

A single link list is a list made up of nodes that consists of two parts.

Basically, a single linked list is a list made up of nodes.

Now, what is a node by the way?

This is how a node looks like.

This node contains two parts.

The one is data, and the other one is link.

Data part contains the actual data

and link part contains the address of the next node of the list.

If you ask me how linked list is made,

I will simply give you this answer,

that a linked list is made up of nodes.

Now, we will see how to represent a single linked list.

Suppose we want to store a list of numbers.

These are the list of numbers we are available with, 23, 54, 78, and 90

For this purpose, I need to create four different nodes.

Because we have four different numbers to store,

we need to create a list of four different nodes.

The first node contains the data 23,

the second node contains the data 54,

third node contains the data 78,

and fourth node contains data 90.

Now, I would like to tell you that these nodes

need not be stored in sequential order in memory.

This should be well noted.

For the simplicity sake, I have taken these addresses.

The first node address is 1000,

second node address is 2000,

third node address is 3000,

and fourth node address is 4000.

And you can see, the addresses need not be sequential.

This is not an array, this is a linked list.

Now of course, there is something missing out here.

This list is incomplete.

Obviously, the list has not been created upto now.

Because, there is some way to reach the next node of the list

and in order to do that, we will store

the addresses in the link part of each and every node.

How it looks like, let's see.

These are the addresses which we will store in the link part.

You can see, that the first node contains this address that is 2000,

which is the address of the second node of the list.

Isn't that so?

From the first node, I can easily reach the next node

if I have this address. That is why,

I have stored this address over here.

From the second node, I can easily the third node.

Because, the address stored here is 3000,

which is the address of the third node of the list.

And third node contains the address 4000,

which is the address of the last node of the list.

And last node contains NULL, which means

it is not containing any address.

It will simply not point to anything.

And it indicates that this is the last node, right?

So basically, with the help of link part of the node,

we can reach the next node of the list.

I am representing the link between

these nodes using these arrows.

But you may ask this question that,

how to access the first node of the linked list?

If we have the address of the first node,

we can reach the rest of the nodes, right?

But, how to access the first node of the linked list?

In order to access the first node of the linked list,

we need a pointer.

With the help of pointer, we can access

the first node of the list, if it contains

the address of the first node.

I am naming this pointer as head.

And in the rest of the lectures, we will also see

that the name of this pointer will remain head.

Because, it is the pointer to the first node of the list.

By using this pointer, we can

access the first node of the list.

And from the first node, we can access the second node and so on.

So basically, this whole list is now accessible.

As this pointer contains the address 1000,

so I am using this arrow, which represents that

this pointer contains the address of the first node.

After seeing how a single linked list looks like,

we will see how to create a single linked list programmatically

and how to perform different operations in

single linked list and other linked list

in the same way as we do in the case of arrays.

Okay friends, this is it for now.

Thank you for watching this presentation.