Delete Node at Beginning in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

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What does 'Delete Node at Beginning' mean in a linked list?

It means removing the first node of the linked list and making the second node the new head.

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Why do we need to update the head pointer when deleting the first node?

Because the head points to the first node, and after deletion, the head must point to the new first node to keep the list connected.

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What happens if we delete the first node in a list with only one node?

The list becomes empty, so the head pointer is set to null (or None in Python).

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Show the Python code snippet to delete the first node of a singly linked list.

if head is not None: head = head.next

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What is the time complexity of deleting the first node in a singly linked list?

O(1) because it only involves changing the head pointer to the next node.

What pointer do you update when deleting the first node in a singly linked list?

A Head pointer

B Tail pointer

C Next pointer of last node

D Previous pointer

The head pointer must be updated to point to the second node after deleting the first node.

What happens if you delete the first node in an empty linked list?

A Head points to null

B List becomes empty

C Tail pointer changes

D Error or no change

If the list is empty, there is no node to delete, so either an error occurs or nothing changes.

What is the time complexity of deleting the first node in a singly linked list?

A O(log n)

B O(1)

C O(n)

D O(n^2)

Deleting the first node is a constant time operation because it only involves updating the head pointer.

After deleting the first node, what does the new head point to?

A The second node

B The last node

C Null

D The deleted node

The new head points to the second node, which becomes the first node after deletion.

If the linked list has only one node and you delete it, what is the new head?

A The same node

B The next node

C Null (None)

D The tail pointer

Deleting the only node makes the list empty, so the head is set to null (None).

Explain step-by-step how to delete the first node in a singly linked list.

Think about what the head points to before and after deletion.

Write a simple Python function to delete the first node of a singly linked list and return the new head.

Remember to handle the empty list case to avoid errors.