What is the effect of maintaining a tail pointer on the amortized cost of append operations when the list is used as a queue?

• A. Enables O(1) amortized append by avoiding traversal to the end
• B. Makes append slower due to extra pointer updates
• C. Has no effect on cost
• D. Increases space consumption without benefit

Answer: (A)

Keeping a tail pointer lets you add at the end in constant time, which makes each append operation O(1) and thus O(1) amortized when the list is used as a queue. With a tail pointer you directly link the new node after the current tail and update the tail reference; you don’t need to walk from the head to the last node. Without a tail pointer, every append would require traversing to the end, making the cost proportional to the list length and hurting the amortized cost over a sequence of operations. The tail pointer adds a tiny constant-space overhead (one extra reference) but provides a real time gain. So maintaining the tail pointer enables O(1) amortized append by avoiding traversal.