If the node to delete is known, what operation becomes possible in constant time?

• A. Inserting at head
• B. Deleting that node
• C. Reversing the list
• D. Searching for a node by value

Answer: (B)

Knowing exactly which node to delete removes the need to search through the list. Deletion in a linked list usually requires locating the node and its predecessor to relink the list, which takes traversal time. If you have a direct reference to the node to remove, you can unlink it immediately by adjusting pointers, effectively removing it in constant time. In a singly linked list, this is straightforward when you can update the previous node’s next pointer, or by the common trick of copying data from the next node into the current node and bypassing the next node (provided the node to delete isn’t the last one). So the operation that becomes possible in constant time is deleting that specific node.