Edge-case handling when deleting nodes at the head of a singly linked list: how does a dummy head affect the process?

• A. Without a dummy head you must update the head pointer; with a dummy head this is simplified
• B. Deleting the head is not allowed
• C. The dummy head makes deletions at the head more complex
• D. The head always points to itself

Answer: (A)

The key idea is that a dummy head provides a fixed predecessor for every real node, including the head, so deletion logic can be uniform without special-casing the first node. With a dummy node at the front, you keep a prev pointer starting at the dummy. When you delete any node, you simply set prev.next to current.next, effectively skipping the node to be removed. If you’re removing the real head, prev is still the dummy, so dummy.next is updated to head.next. After the operation, the true head of the list is dummy.next, so you always have a consistent way to re-link the list.

For example, with a list like dummy -> 5 -> 7 -> 9, deleting the head 5 sets dummy.next to 7. The actual head becomes dummy.next, and you didn’t need any separate logic to handle the head case. Without a dummy, you’d typically have to update the real head pointer directly, which can complicate the code and require different branches for head vs. non-head deletions.

So using a dummy head makes edge-case deletions at the head simpler and more uniform.