Pop Using Linked List Node in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the 'pop' operation do in a linked list?

It removes the first node (head) from the linked list and returns its value.

beginner

In a singly linked list, what pointer is updated when popping the head node?

The head pointer is updated to point to the next node after the current head.

beginner

Why must we check if the linked list is empty before popping?

Because popping from an empty list would cause an error or return None since there is no node to remove.

intermediate

What is the time complexity of popping the head node in a singly linked list?

O(1) because it only involves updating the head pointer and returning the removed node's value.

beginner

Show the steps to pop a node from a linked list with nodes: 10 -> 20 -> 30 -> null.

1. Save the current head node (10).<br>2. Update head to next node (20).<br>3. Return value 10.<br>Resulting list: 20 -> 30 -> null.

What happens to the head pointer after popping a node from a linked list?

A It points to the removed node.

B It points to the next node after the removed node.

C It becomes null always.

D It points to the last node.

After popping, the head pointer moves to the next node in the list.

What is the value returned by the pop operation on a linked list?

A The total number of nodes.

B The value of the last node.

C The value of the removed head node.

D Always None.

Pop returns the value stored in the removed head node.

What should you do if you try to pop from an empty linked list?

A Return None or indicate the list is empty.

B Remove the last node.

C Add a new node.

D Throw an error without checking.

Popping from an empty list should safely return None or a similar indication.

What is the time complexity of popping the head node in a singly linked list?

A O(1)

B O(n)

C O(log n)

D O(n^2)

Popping the head node is a constant time operation.

If the linked list is 5 -> 15 -> 25 -> null, what is the list after one pop?

A null

B 5 -> 15 -> 25 -> null

C 25 -> null

D 15 -> 25 -> null

The head node 5 is removed, so the new head is 15.

Explain how the pop operation works on a singly linked list.

Think about what happens to the head and what value you get back.

Describe the steps and changes in the linked list when popping a node from 1 -> 2 -> 3 -> null.

Visualize removing the first node and shifting the head.