How would you implement a function that returns a new reversed list without modifying the original list?

• A. Use a recursive approach that mutates the original.
• B. Create new nodes while traversing the original and prepend to a new list.
• C. In-place reverse by re-linking nodes.
• D. Swap data values in original nodes.

Answer: (B)

The key idea is to produce a new list without touching the original data. To do this, you walk through the existing list, and for each node you create a fresh node with the same value, then insert that new node at the front of a new result list. By prepending, the order naturally becomes reversed, so after you’ve processed all nodes, you have a reversed copy while the original remains unchanged. This approach preserves immutability of the input and yields a separate list that is the reverse of the original.

Why the other approaches don’t fit here: mutating the original during a traversal would alter the input, which violates the requirement to keep the original list intact. Re-linking the original nodes in place achieves reversal but changes the original structure. Swapping data values in the original nodes changes the contents of the original data and doesn’t create a new list; it also fails to meet the goal of returning a separate reversed list.

So creating new nodes while traversing and prepending to a new list provides a reversed copy without modifying the original. It’s O(n) time with O(n) extra space, since you allocate a new node for each element.