1 Chapter 16-1 Linked Structures Dale/Weems

2 Chapter 16 Topics l Meaning of a Linked List l Meaning of a Dynamic Linked List l Traversal, Insertion and Deletion of Elements in a Dynamic Linked List l Specification of a Dynamic Linked Sorted List l Insertion and Deletion of Elements in a Dynamic Linked Sorted List

3 What is a List? l A list is a varying-length, linear collection of homogeneous elements l Linear means that each list element (except the first) has a unique predecessor and each element (except the last) has a unique successor

4 To implement the List ADT The programmer must 1) choose a concrete data representation for the list, and 2) implement the list operations

5 Recall: 4 Basic Kinds of ADT Operations l Constructors -- create a new instance (object) of an ADT l Transformers -- change the state of one or more of the data values of an instance l Observers -- allow client to observe the state of one or more of the data values of an instance without changing them l Iterators -- allow client to access the data values in sequence

List Operations Transformers n Insert n Delete n Sort Observers n IsEmpty n IsFull n Length n IsPresent change state observe state 6

7 ADT List Operations Iterator n Reset n GetNextItem l Reset prepares for the iteration l GetNextItem returns the next item in sequence l No transformer can be called between calls to GetNextItem (Why?) Iteration Pair

8 Array-based class List Reset IsFull Length IsPresent Delete IsEmpty Insert GetNexItem Private data: length data [ 0] [1] [2] [MAX_LENGTH-1] currentPos SelSort

9 // Specification file array-based list (“list.h”) const int MAX_LENGTH = 50; typedef int ItemType; class List // Declares a class data type { public: // Public member functions List(); // constructor bool IsEmpty () const; bool IsFull () const; int Length () const; // Returns length of list void Insert (ItemType item); void Delete (ItemType item); bool IsPresent(ItemType item) const; void SelSort (); void Reset (); ItemType GetNextItem (); private: // Private data members int length; // Number of values currently stored ItemType data[MAX_LENGTH]; int CurrentPos; // Used in iteration }; 9

10 Implementation Structures l Use a built-in array stored in contiguous memory locations, implementing operations Insert and Delete by moving list items around in the array, as needed l Use a linked list in which items are not necessarily stored in contiguous memory locations l A linked list avoids excessive data movement from insertions and deletions

11 Implementation Possibilities for a List ADT List Linked list Built-in array Built-in dynamic data and pointers Built-in array of structs

12 Array Representation of a Linked List 2 head component link Node[0] Node[1] Node[2] Node[3] Node[4] Node[5] Node[6] Node[7]

13 Data Structure of Array Based Linked List struct NodeType { int component; int link; }; NodeType node[1000]; // Max nodes int head;

14 Insert a New Node into a Linked List 2 head component link Node[0] Node[1] Node[2] Node[3] Node[4] Node[5] Node[6] Node[7] Insert 25, Setting link to 7 Change link from 7 to 1

15 Delete a Node from a Linked List 2 head component link Node[0] Node[1] Node[2] Node[3] Node[4] Node[5] Node[6] Node[7] Change the link From 4 to 0 Deleted

16 A Linked List l A linked list is a list in which the order of the components is determined by an explicit link member in each node Each node is a struct containing a data member and a link member that gives the location of the next node in the list head ‘X’ ‘C’ ‘L’

17 Dynamic Linked List head “Ted” “Irv” “Lee” l A dynamic linked list is one in which the nodes are linked together by pointers and an external pointer (or head pointer) points to the first node in the list

18 Nodes can be located anywhere in memory l The link member holds the memory address of the next node in the list head 3000 “Ted” 5000 “Irv” 2000 “Lee” NULL

19 // Type declarations struct NodeType { char component; NodeType* link; } typedef NodeType* NodePtr; // Variable DECLARATIONS NodePtr head; NodePtr ptr; 19 Declarations for a Dynamic Linked List. component. link ‘A’ 6000

20 Pointer Dereferencing and Member Selection. Component. link ‘A’ 6000 ptr. component. link ‘A’ 6000 *ptr ptr. component. link (*ptr).component ptr->component ‘A’ 6000

21 ptr is a pointer to a node. component. link ‘A’ 6000 ptr

22 *ptr is the entire node pointed to by ptr ptr. component. link ‘A’ 6000 *ptr

23 ptr->component is a node member ptr. component. link ptr->component (*ptr).component // Equivalent ‘A’ 6000

24 ptr->link is a node member ptr. component. link ptr->link (*ptr).link // Equivalent ‘A’ 6000

25 Traversing a Dynamic Linked List // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component // Or, do something else with node *ptr ptr = ptr->link; } ptr 3000 “Ted” 5000 “Irv” 2000 “Lee” NULL head

26 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

27 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

28 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

29 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

30 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

31 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

32 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

33 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

34 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

35 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr NULL 3000 “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

36 // Pre: head points to a dynamic linked list ptr = head; while (ptr != NULL) { cout component; // Or, do something else with node *ptr ptr = ptr->link; } ptr NULL 3000 “Ted” 5000 “Irv” 2000 “Lee” NULL head Traversing a Dynamic Linked List

37 The End of Chapter 16 Part 1