What is the role of the tail pointer in a linked list?

• A. Points to the head node
• B. Points to the last node to optimize end insertions
• C. Stores the list length
• D. Points to null to indicate end

Answer: (B)

The tail pointer is a reference to the last node in the list. This makes adding at the end very fast: you simply link the current last node to the new node and move the tail reference to that new node, all in constant time. Without a tail pointer, you’d have to start at the head and traverse to the end each time you append, which is linear time.

In a typical setup, the list has a head pointer to the first node and a tail pointer to the last node. When the list is empty, both are null; when you insert the first element, you update both head and tail to that node. The tail itself points to the last node, not to the null terminator. The null you see at the end is the next field of the last node, not the tail pointer. This is why the tail pointer is so useful for end insertions.