Linked Lists

Tarun Luthra

Agenda

What you will learn?

  • Classes & Objects Revision

  • What are Linked Lists ?

  • Basic Functionality

Classes & Objects Revision

class Node:
    x = 0
    y = 0

Classes & Objects Revision

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()


main()

Classes & Objects Revision

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    print(n1.x) # 0
    print(n1.x) # 0


main()

Classes & Objects Revision

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20
    print(n1.x) # 50
    print(n1.y)	# 20


main()

Classes & Objects Revision

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = n1

    print(n1.x)
    print(n1.y)


main()

Classes & Objects Revision

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = n1
    n2.x = 100

    print(n1.x)
    print(n1.y)


main()

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = n1
    n2.x = 100

    n3 = n1

    print(n3.x)  # 100
    print(n3.y)  # 20


main()

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = n1
    n2.x = 100

    n3 = n1

    print(n3.x)  # 100
    print(n3.y)  # 20

    n4 = Node()


main()

Constructors

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = Node()
    n2.x = -20
    n2.y = 10


main()

Constructors

class Node:
    x = 0
    y = 0


def main():
    n1 = Node()
    n1.x = 50
    n1.y = 20

    n2 = Node()
    n2.x = -20
    n2.y = 10


main()

class Node:
    x = 0
    y = 0

    def __init__(self, a, b):
        self.x = a
        self.y = b


def main():
    n1 = Node(50, 20)

    n2 = Node(-20, 10)


main()

Can we have an object reference as a property ? 🧐

The 'next' property

class Node:
    data = 0
    next = None

The 'next' property

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None

The 'next' property

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)


main()

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)


main()

data

next

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)


main()

data

next

10

null

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)


main()

data

next

10

null

t1

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)


main()

data

next

10

null

t1

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)


main()

data

next

10

null

t1

data

next

20

null

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)


main()

data

next

10

t1

data

next

20

null

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)

    t2 = t1.next


main()

data

next

10

t1

data

next

20

null

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)

    t2 = t1.next


main()

data

next

10

t1

data

next

20

null

t2

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)

    t2 = t1.next
    t2.next = Node(30)


main()

data

next

10

t1

data

next

20

null

t2

data

next

30

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)

    t2 = t1.next
    t2.next = Node(30)
    t2 = t2.next

    print(t2.data)


main()

data

next

10

t1

data

next

20

null

t2

data

next

30

class Node:
    data = 0
    next = None

    def __init__(self, x):
        self.data = x
        self.next = None


def main():
    t1 = Node(10)
    t1.next = Node(20)

    t2 = t1.next
    t2.next = Node(30)
    t2 = t2.next

    print(t2.data)  # 30


main()

data

next

10

t1

data

next

20

null

t2

data

next

30

data

next

10

t1

data

next

20

null

t2

data

next

30

data

next

10

t1

data

next

20

null

t2

data

next

30

We only need head Node address to access entire chain of data.

data

next

10

t1

data

next

20

null

t2

data

next

30

This type of data structure is called a 

data

next

10

t1

data

next

20

null

t2

data

next

30

This type of data structure is called a 

Linked List

data

next

10

t1

data

next

20

null

data

next

30

Linked List

A Linked List is a linear data structure consisting of connected nodes where each node has corresponding data and a pointer to the address of the next node.

 

The first node of a linked list is called the Head, and it acts as an access point.

Time to try!

Let's begin!

Given N > 0, create a linked list which contains data from 1 to N.

Given N > 0, create a linked list which contains data from 1 to N.

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

null

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 2

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 2

data

next

2

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 2

data

next

2

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 3

data

next

2

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 3

data

next

2

data

next

3

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 3

data

next

2

data

next

3

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 4

data

next

2

data

next

3

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 4

data

next

2

data

next

3

data

next

4

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

i = 4

data

next

2

data

next

3

data

next

4

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Given N > 0, create a linked list which contains data from 1 to N.

n = 4

data

next

1

head

temp

null

return head

data

next

2

data

next

3

data

next

4

def generateLL(n):
    head = Node(1)
    temp = head

    for i in range(2, n + 1):
        temp.next = Node(i)
        temp = temp.next
    return head

Size of a Linked List 👨‍💻 

Given the head of a linked list, return its size

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

null

data

next

2

data

next

3

data

next

4

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

Given the head of a linked list, return its size

int size(Node head) {
    Node temp = head;
    int count = 0;
    while (temp != null) {
        count++;
        temp = temp.next;
    }
    return count;
}
def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 0

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 1

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 1

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 2

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 2

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 3

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 4

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

count = 4

Given the head of a linked list, return its size

def size(head):
    temp = head
    count = 0
    while temp != None:
        count += 1
        temp = temp.next
    return count

data

next

1

head

temp

null

data

next

2

data

next

3

data

next

4

return count

count = 4

Insertion

Given the head node of a linked list, insert a new node at kth index (0 based indexing)

Given the head node of a linked list, insert a new node at kth index (0 based indexing)

def insert(head, pos, data):
    if pos < 0 or pos > size(head):
        return head

    temp = head
    newNode = Node(data)

    if pos == 0:
        newNode.next = head
        return newNode

    for i in range(pos - 1):
        temp = temp.next

    newNode.next = temp.next
    temp.next = newNode
    return head

Deletion

Given the head of a linked list, delete the kth node.

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

Loop will run only one iteration

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Loop will run only one iteration

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

30

data

next

40

0

1

2

3

pos = 2

temp

This node is not referred by any reference. It will be cleaned by the garbage collector.

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

40

0

1

2

3

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

40

0

1

2

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Given the head of a linked list, delete the kth node.

data

next

10

head

null

data

next

20

data

next

40

0

1

2

pos = 2

temp

def remove(head, pos):
    if pos < 0 or pos > size(head):
        return head

    if pos == 0:
        return head.next

    temp = head
    for i in range(pos - 1):
        temp = temp.next

    temp.next = temp.next.next
    return head

Codes 👨‍💻 

Python -

https://ide.codingminutes.com/?id=aik

Problems to Practice 👨‍💻 

  1. Print Linked List
  2. Insert at head
  3. Insert at tail
  4. Insert at specific position
  5. Delete a node
  6. Get Node Value
  7. Print in Reverse
  8. Compare two lists

Thank you! 👨‍💻 

Linked Lists Basics - Python

By Tarun Luthra

Made with Slides.com

Linked Lists Basics - Python

  • 224

More from Tarun Luthra