Link list

SupervisedDr Nuri

Prepared by Didar Rashad

2014-2015

Linked Lists

Linked Lists 2

Link list in data structure

Introduction to Linked List

1.Link list is a data Structure which consists of group of nodes that forms a sequence.2. Linked list is group of nodes in which each node have link to next node to form a chain,

Linked List definition

1. Linked List is Series of Nodes2. Each node Consist of two Parts  Data Part & Pointer Part3. Data part stores value of node Pointer Part stores the address of the next node

Linked List Types Singly Linked list Circular singly linked list Doubly linked lists Circular doubly linked lists

Singly Linked List

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Singly Linked list Each Node contain address of the next node to be

followed. In Singly Linked List only Linear or

Forward Sequential  movement is possible. Elements are accessed sequentially , no direct

access is allowed. First Node does not have predecessor while last

node does not have any successor. We can have multiple data fields inside Node but we

have only single “Link” for next node.

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Circular Singly Linked ListLast node contains the address of the first node First

Circular Singly Linked List

Doubly linked lists

In Doubly Linked List , each node contain two address fields .

One address field for storing address of next node to be followed and second address field contain address of previous node linked to it.

So Two way access is possible ,We can start accessing nodes from start as well as from last .

Like Singly Linked List also only Linear but Bidirectional  Sequential  movement is possible.

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Circular Doubly Linked listContains the address of first node and last node

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Difference Between array and Linked List

Access Random\sequential

Memory Structure

Memory Allocation

Insert\ deletion

Difference Between array

and Linked List

array elements can be randomly Accessed using Subscript Variable, a[0],a[1],a[3] can be randomly accessed

While In Linked List We have to Traverse Through the Linked List for Accessing Element. So O(n) Time required for Accessing Element .Generally In linked List Elements are accessed Sequentially.

Access Random\sequential

Memory Structure

But link list is not necessary to store next element at the Consecutive memory Location In link list Element is stored at any available Location , but the Pointer to that memory location is stored in Previous Node.

array is stored in contiguous Memory Locations , i.e Suppose first element is Stored at 2000 then Second Integer element will be stored at 2001 .

As the Array elements are stored in  contiguous memory Locations , so While Inserting elements ,we have to create space for Insertion.So More time required for Creating space and Inserting ElementSimilarly We have to Delete the Element from given Location and then Shift All successive elements up by 1 position

Insert\ deletion

In Linked List we have to Just Change the Pointer address field (Pointer),So Insertion and Deletion Operations are quite easy to implement

Insert\ deletion

Memory Should be allocated at Compile-Time in array . at the time when Programmer is Writing Program,array uses Static Memory Allocation

In Linked list memory can be allocated at Run-Time , After executing ProgramLinked List Uses Dynamic Memory Allocation

Memory Allocation

Advantages of linked list1.Linked List is Dynamic data Structure .

Linked List Data Structure is Dynamic in nature.

just create Linked List structure and memory will be allocated at run time.

while running program at run time we can allocate much memory.

Oslo we can allocate any number of nodes .Because this link list can grow and shrink during run time.

2. Insertion and Deletion Operations are Easier

Advantages of linked list3. Efficient Memory Utilization , no need to pre-allocate memory

we don’t have to allocate memory at compile time.

Memory is allocated at run time, so that Linked list data structure provides us strong command on memory utilization.

4. Faster Access time , can be expanded in constant time without memory overhead5. Linear Data Structures such as array , Queue can be easily implemented by using Linked list

Disadvantages of linked list1. Wastage of memory

. Pointer Requires extra memory for storage.

Suppose we want to store 3 integer data items then we have to allocate memory -

in case of array

Memory Required in Array = 3 Integer * Size

=3 * 2 bytes

= 6 bytes

Memory Required in LL = 3 Integer * Size of Node

= 3 * Size of Node Structure

= 3 * Size(data + address pointer)

= 3 * (2 bytes + x bytes)

= 6 bytes + 3x bytes

Disadvantages of linked list

2. No random AccessIn Linked list no random access is given to user, we have to access each node sequentially.

3. Heap space restrictionWhenever memory is dynamically allocated , It utilizes memory from heap.

Memory is allocated to Linked List at run time if only there is space available in heap.

If there is insufficient space in heap then it can’t create any memory.

4. Reverse Traversing is difficultIn case if we are using singly linked list then it is very difficult to traverse linked list from end.

If using doubly linked list then though it becomes easier to traverse from end to start

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Insertion Doubly linked lists

A B X C

A B C

p

A B C

p

X

q

p q

Linked Lists 22

Deletion Doubly linked lists

A B C D

p

A B C

D

p

A B C

Thank you