Understanding deletion before a given node

Deleting a node before the given node is an operation that gives a doubly linked list a significant advantage over a singly linked list. In a singly linked list, the implementation of this operation is complicated as it requires keeping a previousToPrevious reference variable to delete the node before a given node.

However, in a doubly linked list, we can access the nodes in the reverse direction using the previous pointer stored in every node, making the entire operation much simpler. Let's examine all the possible cases for deleting a node before the given node in a doubly linked list.

1. The list is empty

If the list is empty and contains no elements, we cannot find the given node because it does not exist within the list. Deleting the node before the given node is not possible because there is no reference point within the list to perform the deletion. In this case, we can return the existing head, as the list is empty, and no node needs to be deleted.