Question

The following is an excerpt from the code to a singly linked list implementation from Data Structures and Algorithms in C++ (2nd Edition) by Adam Drozdek that involves deleting a node with a given value.

IntNode *tmp = head->next;
head = head->next;
delete tmp;

(head is defined elsewhere as an IntNode*) Are there typos in this code fragment, or is my mental processor incorrect in that head will always be a null pointer after every execution of the above code fragment?

Answer 1

When you write delete tmp, you are deleting the object pointed to by tmp. However, after deleting head will still point to the same place. Dereferencing it (*head) will cause problems, because the object head is pointing to has been deleted.