What is the defining feature of a threaded linked list that enables traversal without recursion?

• A. It uses pointers to in-order successor to move to the next node.
• B. It stores all nodes in a separate array.
• C. It uses backward pointers to previous node.
• D. It clones the list and traverses the clone.

Answer: (A)

Threaded linked lists embed a direct link to the next node in the traversal order, typically the in-order successor. This means every node carries a pointer to the node that should come next when traversing the structure. With these successor pointers, you can walk through the entire list by simply following each node’s successor, in a simple loop, without using recursion or a stack. This threading eliminates the need to backtrack or keep additional state while traversing in the desired order.

Storing all nodes in a separate array would be external to the list’s structure, so it doesn’t inherently enable non-recursive traversal. Backward pointers help with reverse traversal, not the smooth forward in-order traversal without extra mechanisms. Cloning the list and traversing the clone is unnecessary and doesn’t reflect how the threading mechanism provides a built-in non-recursive path through the original structure.