Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

access this node is to start from the head of the list and search all the way through
the list. But such a sequence of link hopping operations could take a long time.
3.3 Doubly Linked Lists
As we saw in the previous section, removing an element at the tail of a singly linked
list is not easy. Indeed, it is time consuming to remove any node other than the head
in a singly linked list, since we do not have a quick way of accessing the node in front
of the one we want to remove. Indeed, there are many applications where we do not
have quick access to such a predecessor node. For such applications, it would be nice
to have a way of going both directions in a linked list.
There is a type of linked list that allows us to go in both directions—forward and
reverse—in a linked list. It is the doubly linked list. Such lists allow for a great
variety of quick update operations, including insertion and removal at both ends, and
in the middle. A node in a doubly linked list stores two references—a next link,
which points to the next node in the list, and a prev link, which points to the
previous node in the list.
A Java implementation of a node of a doubly linked list is shown in Code Fragment
3.17, where we assume that elements are character strings. In Chapter 5, we discuss
how to define nodes for arbitrary element types.
Code Fragment 3.17: Java class DNode representing
a node of a doubly linked list that stores a character
string.
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