What is one clear advantage of maintaining a tail pointer when appending to a linked list?

• A. Append can be performed in O(1) time.
• B. Append requires traversing the entire list.
• C. Memory usage increases by O(n).
• D. It prevents removal of last element.

Answer: (A)

Keeping a tail pointer lets you add a new node in constant time by linking it directly after the current last node and then updating the tail to the new node. This avoids walking from the head to the end each time, so append becomes O(1). Without a tail pointer, you’d have to traverse the entire list to find the last node before attaching the new one, which makes append O(n) for a list of length n. The extra tail reference uses a fixed amount of additional space, so the overall memory usage stays O(1) aside from the nodes themselves. It doesn’t inherently prevent removing the last element; removing the tail may require updating the tail reference or traversing to find the new last node, but it doesn’t negate the benefit of constant-time appends.