Linked Lists Chapter 4

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 CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Preliminaries Issues with Array based implementations of Lists: Insert and Delete require shifting CS 308 Chapter 4 -- Linked Lists

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; CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Example: (a) declaration (b) & (c) * (d) new CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Example (cont): CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Example (cont): CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Example: Pointers also have issues Creation of Garbage Dangling Pointers CS 308 Chapter 4 -- Linked Lists

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]; CS 308 Chapter 4 -- Linked Lists

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? CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Pointer-Based Linked Lists Nodes: Declaration struct Node { int item; Node *next }; Allocation Node *p; p = new Node; CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Usage (*p).item = 3 p->item = 3 Head Node Declaration: Node *head; CS 308 Chapter 4 -- Linked Lists

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. CS 308 Chapter 4 -- Linked Lists

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 CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Deleting a Specified Node from a Linked List General case Special case (prev == NULL) CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Inserting a Node into a Specified Position of a Linked List General case Special Case (prev == NULL) CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Special Case (curr == NULL) CS 308 Chapter 4 -- Linked Lists

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 CS 308 Chapter 4 -- Linked Lists

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) CS 308 Chapter 4 -- Linked Lists

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 CS 308 Chapter 4 -- Linked Lists

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. CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Processing Linked Lists Recursively Traversal void writeList(Node * nodeptr) Insertion void linkedListInsert(Node * & headPtr, ListItemType newItem); CS 308 Chapter 4 -- Linked Lists

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 CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Circular Linked Lists CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Dummy Head Nodes CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Doubly Linked Lists CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists Doubly Linked Lists Insertion Deletion CS 308 Chapter 4 -- Linked Lists

Chapter 4 -- Linked Lists CS 308 Chapter 4 -- Linked Lists