p12 linked list

8/3/2019 p12 Linked List

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Structures Containing PointersStructures Containing Pointers

main()

{

structint int_pointers

{

int *p1;

int *p2;

};struct int _pointers pointers;

int i1 =100, i2;


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pointers.p1 = &i1;

pointers.p2 = &i2;

*pointers.p2 = -97;printf(i1 =%d,*pointers.p1=%d\n,i1,*pointers.p1)

printf(i2 =%d,*pointers.p2=%d\n,i2,*pointers.p2)

}Output:

i1 = 100, *pointers.p1 = 100

I2 = -97, *pointers.p2 = -97


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LINKED LISTLINKED LIST

Linear collection of data elements that

stores a group of values of the same data

type. Dynamic data structures - The successive

elements are not stored at contiguous

memory location.

Stored at a location, wherever they find

the free memory space.


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It is a collection of components, callednodes.

Every node contains the address of the

next node. Every node in a linked list has two

components:

One to store relevant information (data)One to store the address, called link

data link Structure of a node


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A list of items, called nodes, in which theorder of the nodes is determined by the

address, called the link, stored in each

node.45 65 34 76

head

Down arrow in the last node indicates that this link field is

NULL.

Arrow in each indicates that the address of the node to

which it is pointing is stored in that node.


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Linked listsLinked lists

main(){

struct entry

{

int value;struct entry *next;

};

struct entry n1,n2;

n1.next = &n2;}struct entry *next; - Struct entry contains a pointer to an

entry structure called next


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Linked listsLinked listsmain()

{struct entry

{

int value;

struct entry *next;};

struct entry n1,n2,n3;

int i;

n1.value = 100;

n2.value = 200;

n3.value = 300;


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n1.next = &n2;n2.next = &n3;

i = n1.nextvalue;printf (%d , i);

printf (%d\n, n2.nextvalue);} Output: 200 300


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i = n1.nextvalue; - the value member of theentry structure pointed to by n1.next isaccessed and assigned to the integer

variable i.

i = *(n1.next).value

n1.nextvalue is correct and n1.next.value isincorrect as n1.next field contains apointer to a structure


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Basic operations on a list are:

Search the list for a particular item

Insert an item in the list

Delete an item from the list

Using the pointer given to the first node,

we must step through the nodes of the list.


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Inserting an ElementInserting an Element

n2_3 to be inserted after n2 but before n3

struct entry n1, n2, n3, n2_3;

n2_3.next = n2.next;

n2.next = &n2_3;

n2_3 shall be inserted to the list immdiately aftern2 and before n3

Sequence of statements is important.

n2.next = &n2_3; n2_3.next = n2.next not correctas pointer in n2 is overwritten

n2_3 can be anywhere in memory


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Removing an ElementRemoving an Element


n1.next = &n2;

n2.next = &n3;

........

To remove n2 from the list

n1.next = n2.next

This is same as n1.next = &n3

n2 is removed from the list


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Traversing the Linked ListTraversing the Linked List

Normally a Pointer to the linked list is usedfor traversing the entries in the linked list

Pointer is initially set to the start of the list

struct entry *list_pointer = &n1

The end of the list has to be identified

A null pointer (pointer value of 0) is used forsuch a purpose

n3.next = 0;


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Linked List TraversalLinked List Traversalmain()

{struct entry

{

int value;

struct entry *next;};


struct entry *list_pointer = &n1;

n1.value=100; n1.next = &n2;n2.value =200; n2.next = &n3;

n3.value =300; n3.next = 0; (null pointer)


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Traversing through the List

while (list_pointer !=0)

{

printf (%d\n, list_pointervalue);

list_pointer = list_pointernext;

}}

Output = 100 200 300


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Thank you

p12 linked list

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