Placement PreparationLinked List

Shobhit ChaurasiaB.Tech, CSE

Target Audience

People who have coding experience limited to the basic

syntax of C++, pointers and structures, but didn’t take

CS101 seriously and want to learn some basics of coding

quickly.

If you already know how to implement a linked list, then

please spare me the pain of taking a lecture on linked

lists, and volunteer to deliver this lecture.

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 we need to do?

Linked List

head

Node

How to represent a Node in C++ ?

How to represnt integers in C++?

int x;

But Node is a combination of data + pointer

(int) + pointer

(char) + pointer

(string) + pointer

Structures Revisited

Structure variable

stud s;

Access members of struct

s.rollNo = 11010179

s.cpi = 8.1

s.gender = ‘M’

;

How to represent Node in C++

;

Head

Pointer to the first node.Holds the address of the first node in the list

head

Head

Pointer to the first node.

node* head

;

Struct Pointer revisited

Struct Pointer

stud *s;

Access members of struct

s->rollNo = 11010179

s->cpi = 8.1

s->gender = ‘M’rollNo cpi gender

s

;

Accessing data/next node

node* head

Data stored at first node

head->data = ‘a’;

Pointer to second node

head->next

Data stored at second node

(head->next)->data = ‘b’;

head

;

Demo #0(a)

node* temp;

temp = head;

cout<<temp->data;

head

Demo #0(a)

How to go to the second node?

temp = temp->next;

cout<<temp->data;

head

Demo #0(a)

How to go to the third node?

temp = temp->next;

cout<<temp->data;

head

Where’s the list’s end?

headptr

Demo #0(b)

Printing the linked list

Demo #0(b)

Printing the linked list (correct version)

Demo #0(b)

An observation

Demo #0(b) - MORAL

Never move the HEAD while traversing a

linked list

Demo #1

Function to print the 3rd element in linked list

Insert a new node at the end

node* temp;

temp = start;

temp->next == NULL ??

Insert a new node at the end

temp = temp->next;

temp->next == NULL ??

Insert a new node at the end

temp = temp->next;

temp->next == NULL ??

Insert a new node at the end

temp = temp->next;

temp->next == NULL ??

Insert a new node at the end

temp = temp->next;

temp->next == NULL ?? (YES!! Finally reached the end)

Insert a new node at the end

ptr

node* ptr = new node

Insert a new node at the end

ptr

ptr->data = ‘f’;

ptr->next = NULL;

f

Insert a new node at the end

ptr

temp->next = ptr;

Demo #2

Inserting a new node at the end.Discuss 2.cpp

Insert a new node at the start

node* ptr = new node;

ptr

Insert a new node at the start

node* ptr = new node;

ptr->data = ‘z’;

ptrz

Insert a new node at the start

ptr->next = start;

ptr

Insert a new node at the start

start = ptr;

ptr

Demo #3

Insert a new node at the headDiscuss 3.cpp (two methods)

Demo #4

Create a linked list and print its contents.

Demo #5

Same as last problem. Use functions.

Insert after a particular node

Demo #6

Write a function which takes as parameter a

node pointer and inserts a new node after it.

insertInBetween (node* temp)

Deleting first node

Deleting first node

ACTUALLY Deleting first node

ACTUALLY Deleting first node

ACTUALLY deleting first node

ACTUALLY deleting first node

delete frees the memory allocated by new

Demo #7

Write a function to delete the first node of a

linked list.Add this function to 5.cpp

Demo #8

Write a function to delete the last node of

linked listAdd this function to 7.cpp

Delete a node inside the linked list

Delete a node inside the linked list

Locating the node “y”

Can we delete the node “y” now?

Having just the pointer to the node containing

“y” sufficient to delete it?

Break this link, and make it point to the

node “d”

What do we want to do?

Expected Output

What do we need?

Pointer to the previous node

Step 1

prev->next = temp->next;

Step 2

delete temp;

Final output

Demo #9

Delete the node with data = 3Add this function to 5.cpp

Homework

Reverse a linked list.

Linked list vs Arrays

Operation Linked List Array

Insert at start O(1) O(n)

Insert anywhere O(1) O(n)

Delete anywhere O(1) O(n)

Access ith element O(n) O(1)

THANK YOU