What is a circular linked list and how does it differ from a standard singly linked list?

• A. A circular linked list is just a singly linked list with an extra sentinel node.
• B. It forms a closed loop where the last node points back to the head, while a standard singly linked list terminates with NULL.
• C. Circular lists store data in circular buffers.
• D. In circular lists, every node has only a prev pointer.

Answer: (B)

A circular linked list forms a closed loop by making the last node point back to the first node, so there is no NULL to mark the end. In contrast, a standard singly linked list ends with a node whose next pointer is NULL, indicating termination. This means traversal in a circular list can continue indefinitely unless you explicitly detect when you’ve returned to the starting point, while traversal in a regular singly linked list naturally stops when you hit NULL. The idea of a sentinel node isn’t what creates circularity, and circular buffers are a different concept (wrap-around in an array, not a linked list). Also, having every node with a prev pointer describes a doubly linked list, not a characteristic of a circular singly linked list.