Get Length of Linked List in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the length of the linked list after these insertions?

Consider a singly linked list where we insert nodes with values 10, 20, and 30 at the end. What will be the length of the linked list after these insertions?

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if not self.head:
            self.head = new_node
            return
        last = self.head
        while last.next:
            last = last.next
        last.next = new_node

    def get_length(self):
        count = 0
        current = self.head
        while current:
            count += 1
            current = current.next
        return count

ll = LinkedList()
ll.append(10)
ll.append(20)
ll.append(30)
length = ll.get_length()
print(length)

A 3

B 2

C 0

D 1

💡 Hint

Count each node starting from the head until you reach the end (None).

The linked list has three nodes inserted: 10, 20, and 30. The get_length method counts all nodes, so the length is 3.

❓ Predict Output

intermediate

What is the length of the linked list after deleting one node?

Given a linked list with nodes 5 -> 15 -> 25 -> None, if we delete the head node, what will be the length of the linked list?

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if not self.head:
            self.head = new_node
            return
        last = self.head
        while last.next:
            last = last.next
        last.next = new_node

    def delete_head(self):
        if self.head:
            self.head = self.head.next

    def get_length(self):
        count = 0
        current = self.head
        while current:
            count += 1
            current = current.next
        return count

ll = LinkedList()
ll.append(5)
ll.append(15)
ll.append(25)
ll.delete_head()
length = ll.get_length()
print(length)

A 3

B 2

C 0

D 1

💡 Hint

Deleting the head removes the first node, so count remaining nodes.

Initially, the list has 3 nodes. After deleting the head (5), the list becomes 15 -> 25 -> None, which has length 2.

🔧 Debug

advanced

What error occurs when calling get_length on an empty linked list?

Consider the following code where no nodes are added. What happens when get_length is called?

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    def get_length(self):
        count = 0
        current = self.head
        while current:
            count += 1
            current = current.next
        return count

ll = LinkedList()
print(ll.get_length())

A AttributeError

B NoneType error

C 0

D 1

💡 Hint

An empty list has no nodes, so count should be zero.

The head is None, so the while loop does not run and count remains 0. No error occurs.

🧠 Conceptual

advanced

What is the time complexity of the get_length method for a linked list with n nodes?

The get_length method counts nodes by traversing the linked list from head to end. What is its time complexity?

A O(n^2) quadratic time

B O(1) constant time

C O(log n) logarithmic time

D O(n) linear time

💡 Hint

The method visits each node once.

The method visits each of the n nodes once, so the time grows linearly with n.

🚀 Application

expert

After multiple insertions and deletions, what is the final length of the linked list?

Starting with an empty linked list, perform these operations in order: 1. Append 1 2. Append 2 3. Append 3 4. Delete head 5. Append 4 6. Delete head 7. Append 5 What is the length of the linked list now?

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if not self.head:
            self.head = new_node
            return
        last = self.head
        while last.next:
            last = last.next
        last.next = new_node

    def delete_head(self):
        if self.head:
            self.head = self.head.next

    def get_length(self):
        count = 0
        current = self.head
        while current:
            count += 1
            current = current.next
        return count

ll = LinkedList()
ll.append(1)
ll.append(2)
ll.append(3)
ll.delete_head()
ll.append(4)
ll.delete_head()
ll.append(5)
length = ll.get_length()
print(length)

A 3

B 4

C 5

D 2

💡 Hint

Track the list after each operation carefully.

After operations, the list is 3 -> 4 -> 5 -> None, length is 3.