In a doubly linked list, which operation is typically easier to implement efficiently than in a singly linked list?

• A. Appending a new element to the end in constant time.
• B. Deleting a node when you have a reference to that node.
• C. Accessing a middle element by position in constant time.
• D. Searching for a value by traversing backwards only.

Answer: (B)

Removing a node when you have a direct reference is easier in a doubly linked list because each node has both next and previous links. With a pointer to the node to delete, you can splice it out in constant time by linking its predecessor directly to its successor and updating the successor’s previous link to its predecessor, then adjust the head or tail if needed. This avoids any traversal.

In a singly linked list, you only have a next pointer. Without access to the previous node, you must walk from the head to find the node whose next points to the one you want to delete, so the deletion operation can take linear time in the size of the list. The presence of a prev pointer in a doubly linked list makes this unlinking step direct and fast.

The other options don’t offer the same guaranteed constant-time benefit in the common cases: appending to the end can be made constant time in either structure if a tail reference is maintained (not unique to doubly lists), accessing a middle element by position remains O(n) in both, and traversing backwards doesn’t by itself guarantee a faster or simpler deletion in all scenarios.