During a sorted insertion algorithm, which pointer tracks the node just before the current node?

• A. trailCurrent
• B. current
• C. head
• D. tail

Answer: (A)

In a sorted insertion, you must remember the node right before the one you’re examining so you can splice in the new node without losing the rest of the list. This lagging pointer is trailCurrent. As you traverse, you advance current to the next node while updating trailCurrent to the node you just left; this way trailCurrent always points to the node just before current. When you find the correct spot, you can insert by linking trailCurrent.next to the new node and the new node to current, preserving the sorted order. The head simply points to the first element, and the tail to the last, while current is the node currently being looked at.