1. Linked Lists
Chapter 4

2. Chapter 4 -- Linked Lists
This chapter introduces you to C++ pointers and the data structure linked list.
You will see algorithms for fundamental linked list operations such as insertion and deletion.
The chapter also describes several variations of the basic linked list.
As you will see you can use a linked list and its variations when implementing many of the ADTs that appear throughout the remainder of this book
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3. Chapter 4 -- Linked Lists
Preliminaries
Issues with Array based implementations of Lists: Insert and Delete require shifting
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4. Chapter 4 -- Linked Lists
Pointers
A pointer is a data type
A variable can be declared to be a pointer.
int *p;
It stores an address.
Therefore you have to get the address of something
int q;
p= &q;
It has operations.
*p=6;
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5. Chapter 4 -- Linked Lists
Example:
(a) declaration
(b) &
(c) *
(d) new
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6. Chapter 4 -- Linked Lists
Example (cont):
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7. Chapter 4 -- Linked Lists
Example (cont):
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8. Chapter 4 -- Linked Lists
Example:
Pointers also have issues
Creation of Garbage
Dangling Pointers
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9. Chapter 4 -- Linked Lists
Dynamic Allocation of Arrays
Normal allocation (automatic or static)
const int MAX_SIZE = 50;
double anArray[MAX_SIZE];
Dynamic Allocation
int arraySize=50;
double *anArray = new double[arraySize];
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10. Chapter 4 -- Linked Lists
Deleting the memory
delete [ ] anArray;
The name of the array is equivalent to the address of the first element.
anArray == &(anArray[0])
*anArray == anArray[0]
How do you allocate a 2D array dynamically?
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11. Chapter 4 -- Linked Lists
Pointer-Based Linked Lists
Nodes:
Declaration
struct Node {
int item;
Node *next };
Allocation
Node *p;
p = new Node;
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12. Chapter 4 -- Linked Lists
Usage
(*p).item = 3
p->item = 3
Head Node Declaration:
Node *head;
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13. Programming with Linked Lists
The previous section illustrated how you can use pointer variables to implement a linked list
This section begins by developing algorithms
for displaying the data portions of such a linked list.
For inserting and deleting items from a list.
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14. Chapter 4 -- Linked Lists
Displaying the Contents of a Linked List
Suppose we have a list
How do we display it?
The key is making a traversal of the nodes
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15. Chapter 4 -- Linked Lists
Deleting a Specified Node from a Linked List
General case
Special case
(prev == NULL)
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Inserting a Node into a Specified Position of a Linked List
General case
Special Case
(prev == NULL)
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17. Chapter 4 -- Linked Lists
Special Case
(curr == NULL)
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18. Chapter 4 -- Linked Lists
A Pointer Based Implementation of the ADT List
Code was covered last semester, and in Lab 9
Key is shallow vs deep copy
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19. Chapter 4 -- Linked Lists
Comparing Array-Based and Pointer-Based Implementations
Storage:
Arrays are easy to use, but they have a fixed size
An array based implementation is good for a small list.
Access
You can access array items directly with equal access time.
You must traverse a linked list to access its ith node
Insertion and Deletion
Insertion and deletion from a linked list do not require you to shift the data (they do require traversal)
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20. Chapter 4 -- Linked Lists
Saving and Restoring a Linked List by Using a File.
Notes:
Do not write the pointers to the file
Write only its data to a file.
Saving:
Traverse the list and write out the data
Restoring
Read the data and insert at the end of the list
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21. Chapter 4 -- Linked Lists
Passing a Linked List to a Function
A function with access to a linked list’s head pointer has access to the entire list.
Pass the head pointer as a reference argument
Note:
a linked list passed as an argument is not copied, even if its head pointer is passed as a value argument.
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22. Chapter 4 -- Linked Lists
Processing Linked Lists Recursively
Traversal
void writeList(Node * nodeptr)
Insertion
void linkedListInsert(Node * & headPtr, ListItemType newItem);
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23. Variations of the Linked List
This section introduces several variations of the linked list that you have just seen.
Circular Linked Lists
Dummy Head nodes
Doubly Linked Lists
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24. Chapter 4 -- Linked Lists
Circular Linked Lists
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25. Chapter 4 -- Linked Lists
Dummy Head Nodes
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26. Chapter 4 -- Linked Lists
Doubly Linked Lists
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27. Chapter 4 -- Linked Lists
Doubly Linked Lists
Insertion
Deletion
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28. Chapter 4 -- Linked Lists
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