Insert at Specific Position in Doubly Linked List in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a doubly linked list?

A doubly linked list is a chain of nodes where each node has three parts: data, a pointer to the next node, and a pointer to the previous node. This allows traversal in both directions.

beginner

What does 'inserting at a specific position' mean in a doubly linked list?

It means adding a new node at a given place in the list, not just at the start or end. The position is usually counted from the head (start) of the list.

intermediate

What pointers need to be updated when inserting a node in the middle of a doubly linked list?

You must update four pointers: the new node's next and prev, the previous node's next, and the next node's prev, to keep the list connected correctly.

beginner

Why do we check if the position is 1 when inserting in a doubly linked list?

Because inserting at position 1 means adding at the head. We must update the head pointer and handle the previous pointer of the old head.

intermediate

What happens if the position to insert is greater than the length of the doubly linked list?

The insertion is usually done at the end of the list or rejected. It depends on the implementation, but often we add the node at the tail if the position is too large.

Which pointer in a doubly linked list node points to the previous node?

A tail

B prev

C head

D next

The 'prev' pointer points to the previous node in a doubly linked list.

When inserting at position 1 in a doubly linked list, what must be updated?

A Only the tail pointer

B Only the new node's next pointer

C The head pointer and the old head's prev pointer

D No pointers need updating

Inserting at position 1 means adding at the head, so the head pointer and the old head's prev pointer must be updated.

If you want to insert a node at position 3, which nodes' pointers do you need to update?

A Only the new node's pointers

B The head and tail nodes

C No nodes need pointer updates

D The node at position 2 and the node at position 3

You update the new node's pointers and the pointers of nodes at positions 2 and 3 to link the new node correctly.

What happens if you insert at a position greater than the list length?

A Node is inserted at the end

B Insertion fails always

C Node is inserted at the head

D List gets corrupted

Usually, if the position is beyond the list length, the node is inserted at the end.

Which of these is NOT a step when inserting a node in the middle of a doubly linked list?

A Delete the node at the position

B Update new node's next and prev pointers

C Update next node's prev pointer

D Update previous node's next pointer

Deleting a node is not part of insertion; insertion involves updating pointers to add a new node.

Explain step-by-step how to insert a new node at a specific position in a doubly linked list.

Think about how pointers connect nodes before and after the new node.

What pointer updates are necessary when inserting a node between two existing nodes in a doubly linked list?

Focus on the four pointers that keep the chain connected.