What is a threaded linked list and what advantage does threading provide?

• A. A threaded list stores data using two separate arrays.
• B. A threaded list adds pointers to in-order successor to enable traversal without recursion; speeds in-order traversal.
• C. Threading means using multiple threads for traversal.
• D. Threaded lists are singly linked lists with extra back pointers to head.

Answer: (B)

Threaded linked lists add special pointers, called threads, that point to the in-order successor (and sometimes predecessor) of a node. This design lets you walk through the nodes in their in-order sequence without using recursion or a stack.

The advantage is that in-order traversal becomes simple and fast. By following these successor threads from one node to the next, you can traverse the entire structure in order with only constant extra space and no backtracking, which avoids the overhead of recursive calls or maintaining an explicit stack.

Other options don’t fit because they describe completely different ideas: storing data in two arrays is not about threading pointers; threading is not about using multiple OS threads for traversal; and adding back pointers to the head describes a different enhancement than the in-order successor threading used to streamline traversal.