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Chapter 16-1
Linked Structures
Dale/Weems
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Chapter 16 Topics
Meaning of a Linked List Meaning of a Dynamic Linked List Traversal, Insertion and Deletion of Elements
in a Dynamic Linked List Specification of a Dynamic Linked Sorted List Insertion and Deletion of Elements in a
Dynamic Linked Sorted List
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What is a List?
A list is a varying-length, linear collection of homogeneous elements
Linear means that each list element (except the first) has a unique predecessor and each element (except the last) has a unique successor
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To implement the List ADT
The programmer must
1) choose a concrete data representation for the list, and
2) implement the list operations
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Recall:4 Basic Kinds of ADT Operations
Constructors -- create a new instance (object) of an ADT
Transformers -- change the state of one or more of the data values of an instance
Observers -- allow client to observe the state of one or more of the data values of an instance without changing them
Iterators -- allow client to access the data values in sequence
List Operations
Transformers Insert Delete Sort
Observers IsEmpty IsFull Length IsPresent
change state
observe state
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ADT List Operations
Iterator Reset GetNextItem
Reset prepares for the iteration GetNextItem returns the next item in
sequence No transformer can be called between calls
to GetNextItem (Why?)
Iteration Pair
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Array-based class List
Reset
IsFull
Length
IsPresent
Delete
IsEmpty
Insert
GetNexItem
Private data:
lengthdata [0] [1] [2]
[MAX_LENGTH-1]
currentPos
SelSort
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// 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 membersint length; // Number of values currently storedItemType data[MAX_LENGTH];
int CurrentPos; // Used in iteration };
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Implementation Structures
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
Use a linked list in which items are not necessarily stored in contiguous memory locations
A linked list avoids excessive data movement from insertions and deletions
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Implementation Possibilities for a List ADT
List
Linked listBuilt-in array
Built-in dynamic data and pointers
Built-in arrayof structs
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Array Representation of a Linked List
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head 58 -1
4 5
46 0
16 7
39 4
component link
Node[0]
Node[1]
Node[2]
Node[3]
Node[4]
Node[5]
Node[6]
Node[7]
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Data Structure of Array Based Linked List
struct NodeType
{
int component;
int link;
};
NodeType node[1000]; // Max. 1000 nodes
int head;
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Insert a New Node into a Linked List
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head 58 -1
25 7
4 5
46 0
16 1
39 4
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
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Delete a Node from a Linked List
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head 58 -1
25 7
4 5
46 0
16 1
39 0
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
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A Linked List
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’
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Dynamic Linked List
head “Ted” “Irv” “Lee”
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
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Nodes can be located anywhere in memory
The link member holds the memory address of the next node in the list
head 3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
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// Type declarations struct NodeType { char component; NodeType* link;}
typedef NodeType* NodePtr;
// Variable DECLARATIONSNodePtr head;NodePtr ptr;
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Declarations for a Dynamic Linked List
. component . link
‘A’ 6000
2020
Pointer Dereferencing and Member Selection
. Component . link
‘A’ 6000 ptr
ptr
ptr
. component . link
‘A’ 6000
*ptr
ptr
. component . link
(*ptr).component
ptr->component
‘A’ 6000
2121
ptr is a pointer to a node
. component . link
‘A’ 6000 ptr
ptr
2222
*ptr is the entire node pointed to by ptr
ptr
. component . link
‘A’ 6000
*ptr
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ptr->component is a node member
ptr
. component . link
ptr->component
(*ptr).component // Equivalent
‘A’ 6000
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ptr->link is a node member
ptr
. component . link
ptr->link
(*ptr).link // Equivalent
‘A’ 6000
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Traversing a Dynamic Linked List
// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr
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head
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 3000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 3000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 3000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 5000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 5000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 5000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 2000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 2000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr 2000
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr NULL
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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// Pre: head points to a dynamic linked list
ptr = head;
while (ptr != NULL)
{
cout << ptr->component;
// Or, do something else with node *ptr
ptr = ptr->link;
}
ptr NULL
3000 “Ted” 5000 “Irv” 2000 “Lee” NULL
3000 5000 2000
head
Traversing a Dynamic Linked List
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The End of Chapter 16 Part 1
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