How do you delete a node with a given value from a singly linked list when you have access to the head pointer?

• A. Find the node and its previous; adjust previous.next; if head matches, update head; free removed node.
• B. Always remove by setting the previous node's next to NULL.
• C. Delete by copying the next node's data into the current node.
• D. Free the node and leave a dangling pointer.

Answer: (A)

To remove a node by value in a singly linked list when you have the head pointer, you must reconnect the list around the node you’re deleting. Start at the head and keep track of the current node and its previous node. When you find a node whose value matches the target, update the links: if you found the node at the head (no previous node), move the head to the next node; otherwise set the previous node’s next to the current node’s next. Then free the current node’s memory. If you don’t find a matching value, leave the list unchanged. This approach maintains the rest of the list and ensures proper memory management, and it operates in linear time.

Edge cases to keep in mind are when the node to delete is the head (the head must be updated) and when the node is the last one (the previous node’s next becomes NULL). This method is preferable to simply setting a pointer to NULL or to copying data from the next node, which can either truncate the list, cause issues if you can’t access the previous node, or leave a dangling reference.