Worksheet 11: Linked List Deque Name:
An Active Learning Approach to Data Structures using C
1
Worksheet 11: Linked List Deque
In this lesson and the following we will develop a reasonably complete linked list
abstraction. Our list will use sentinels on both the front and the back of the list,
and double links. In this lesson we will emphasize the deque aspects of the list.
In the following lesson we will add more operations.
A deque, you recall, allows
insertions at both the
beginning and the end of the
container. The interface is
shown at right.
Sentinels ensure the list is
never completely empty.
They also mean that all
instructions can be described
as special cases of more
general routines. One of
these, removeLink, you
developed in the previous
lesson. Another internal
routine, addBefore, can be
described as “insert a new
link immediate before an existing link”. Write this new routine, and then show how
all insertions can be handled by this one routine. As you add and remove
elements make sure you keep the value of the size field up to date. When a value
is removed from a list make sure you free the associated link fields. Use an
assertion to check that allocations of new links are successful, and that you do
not attempt to remove a value from an empty list.
Finish the implementation of the LinkedList based on these ideas:
backSentinel
frontSentinel
sentinel
7
4
Sentinel
struct list {
int size;
struct dlink *frontSentinel;
struct dlink *backSentinel;
};
void listInit (struct list *lst);
void listDestroy (struct list *lst);
void listAddFront (struct list *lst, EleType d);
void listAddBack (struct list *lst, EleType d);
void listRemoveFront (struct list *lst);
void listRemoveBack (struct list *lst);
EleType listFront (struct list *lst);
EleType listBack (struct list *lst);
int listSize (struct list *lst);
