DATA STRUCTURE

Ali Abdul Karem Habib

MSc.IT

POINTER A pointer is a variable which represents the

location of a data item . We can have a pointer to any variable type.

Pointer Operators- The address operator & gives the

``address of a variable''. - The indirection operator * gives the

``contents of an object pointed to by pointer''.

To declare a pointer to a variable do:    int *ptr;

POINTER IN C++ Declare pointers to any data type using dereference

operator *int* int_ptr;char* ch_ptr;A pointer takes its value as the address in memory of

another variable

int b, a = 6;int* a_ptr;

a_ptr = &a; /* ‘&’ : address of operator */

B= *a_ptr ; /* ‘*’ : dereference operator */

6

address of ‘a’

a

a_ptr

POINTER EXAMPLE

Consider the effect of the following code:

   int x = 1, y = 2;

int *ip; /*pointer to an integer*/

  ip = &x; /*assign address of x to

ip*/

y = *ip; /*assign value of x to y*/

x = ip; /*assigns address of x to

x*/

*ip = 3; /*assigns 3 to value of x*/

EXAMPLE OF POINTER IN C++ # include < iostream.h >

Void main () {

Int a =30, *ptr ; ptr=&a; Cout<<“ Print the address Of a “<<endl; Cout<< ptr; Cout<< “ The containt Of a “<< endl; Cout<<*ptr; getch(); }

The new operator p = new int • Dynamic allocation of a memory cell that

cancontain an integer . The delete operator returns dynamically

allocated memory to the system for reuse . A pointer to a deallocated memory (*p) cell is

p = NULL

(a) Declaring pointer variables (b) pointing to statically allocated memory (c) assigning a value(d) allocating memory dynamically (e) assigning a value

(f) copying a pointer(g) allocating memory dynamically and assigning a value(h) assigning NULL to a pointer variable(i) deallocating memory

LINKED LIST

It is another type of data structure which are dynamic allocation .

It is collection of especially designed data elements called nodes linked to one another by means of pointers.

Each node is divided into 2 parts first part contains the Data and the second contains Pointer which points to the next node.

ADVANTAGES OF LINKED LIST OVER ARRAY

Array have a fixed dimension. Once the size of an array is decided it can not be increased during execution.

Array elements are always stored in contiguous memory locations .

Insertion and deletion in array is complex because it requires shifting of elements in array.

It is a dynamic data structure, i.e. a linked list can grow and shrink in size during its lifetime.

The nodes of linked list (elements) are stored at different memory locations .

Insertion and deletion in linked list is easy because it does not requires shifting of elements in it.

OPERATION ON LINKED LIST

Creation :- Creation operation is used to create

a linked list which one node .

Insertion: - Insertion operation is used to insert

a new node at any specified location in the

linked list. A new node may be inserted.

(a) At the beginning of the linked list

(b) At the end of the linked list

(c) At any specified position in between in a

linked list

Deletion :- Same Above

OPERATION ON LINKED LIST … CONT

Traversing : - Traversing is the process of

going through all the nodes from one end to

another end of a linked list.

Searching :- Usually searching operations is

employed not only while a data item is

needed but in case of insertion and deletion

at specified location search operation is

performed before nodes can be inserted or

deleted.

TYPES OF LINKED LIST

Basically we can divide the linked list into the

following three types in the order in which

node are arranged.

Singly linked list

Doubly linked list

Circular linked list

A SINGLY LINKED LIST

is one in which all nodes are linked together in some sequential manner. By single pointer Hence it is also called Linear linked list.

Each node in a singly Linked List has two parts one to hold the data and other to point to address of the successor node (next node).

The problem with this list is that we cannot access the predecessor nodes from the current i.e. we cannot backward traverse in a singly linked list.

CREATE NODE USING C++ A node in a linked list is usually a structstruct Node{ int data ;

Node *next;};

Node * Start , *Cur;

Node *p; // pointer to node p = new Node; // allocate node Note :- Access to the Node elements by Pointer using

-> operator p->data , p->next Access to the Node Structure by reference of structure

using Node item ; item. data , item. next

ALGORITHM TO CREATE FIRST NODE

1- Start 2- If Start=Null then 3- Prepare Node 4- Read data 5- Node ->data= data 6- Node ->next=Null 7- Start = Node 8- Cur = Node 9- End .

Data NullStart

Cur

Node

INSERT AT FIRST 1- Start 2- Prepare Node 3- Read Data 4- Node ->Data=Data 5- Node->next=Start 6- Start=Node 7-End.

Data NullStart

CurData

New Node

INSERT AT LAST 1- Start 2- Prepare Node 3- Read Data 4- Node ->Data=Data 5- Cur ->next=Node 6- Cur=node 7- Cur ->next=Null 8- End

56Start

Cur

7 Null

New Node

INSERT AT ANY POSITION 1- Start 2- Prepare Node 3- Read Data 4- Read Pos 5- Node -> Data=Data 6- temp =start 7- Let Cn=1 8- while( Cn < pos-1) 9- temp=temp-> next 10- Cn=Cn+1 11- End While 12- Node -> next=temp ->next 13- temp ->next=node 14- End

INSERT AT ANY POSITION

New Node

Temp

Temp

DELETE NODE AT FIRST 1-Start 2- temp=Start 3- Start= Start -> next 4- Delete ( temp ) 5- temp=Null 6- End .

StartNew Node

DELETE AT LAST

1- Start 2- Let Temp = Start 3- While ( temp ->next <> Cur) 4- temp=temp ->next 5- End While 6- Delete (Cur) 7- Cur=temp 8-Cur->next=null; 9- temp=null 10- End .

DELETE AT ANY POSITION

1- Start 2- Let Temp=start 3- Read Pos4- Cn=15- while ( Cn< pos – 1 ) 6- temp=temp -> next7- Cn=Cn+1 8- End While 9- p= temp -> next10- temp->next=temp ->next -> next11- Delete (p) 12- p=null 13- end

TRAVERSING

1- Start 2- temp=start 3- While ( temp <> null ) 4- print (temp -> Data ) 5- temp = temp -> next 6- End while 7- End .

SEARCHING

1- Start 2- let temp=start3- Read key4- While ( temp <> null) 5- If ( temp -> Data = key ) then 6- print ( “ Found “)7- else

Print ( “Not Found “ ) 8- temp = temp -> next ) 9- End While 10 - End

ASSIGNMENT Write Algorithm to implement Stack using

SLL Write Algorithm to Implement Queue Using

SLL Write Algorithm to Sorting SLL