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Linked ListLinked List
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Limitations of ArrayLimitations of Array To insert or remove an element at an interior location in an To insert or remove an element at an interior location in an
ArrayList requires shifting of data and is an O(n) operation.ArrayList requires shifting of data and is an O(n) operation.
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Limitations of ArrayLimitations of Array An array has a limited number of elementsAn array has a limited number of elements
routines inserting a new value have to check that there is roomroutines inserting a new value have to check that there is room Can’t increase or decrease its size during executionCan’t increase or decrease its size during execution
Can partially solve this problem by reallocating the array as Can partially solve this problem by reallocating the array as needed (how much memory to add?)needed (how much memory to add?) adding one element at a time could be costlyadding one element at a time could be costly one approach - double the current size of the arrayone approach - double the current size of the array
Array elements are stored in contiguous memory locationsArray elements are stored in contiguous memory locations Always we won’t have enough contiguous memoryAlways we won’t have enough contiguous memory
Q: how do we know what is part of the array?Q: how do we know what is part of the array?A: have the elements keep track of each otherA: have the elements keep track of each other use pointers to connect the elements together as a use pointers to connect the elements together as a LISTLIST of things of things
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Introduction to Linked ListIntroduction to Linked List It is linear collection of data items, called It is linear collection of data items, called nodes – nodes – where linear where linear
order is maintain by means of order is maintain by means of pointerspointers
Where each item contains two parts or fields
Data : Information or actual value of an element
Link : It contains the address to its successor (and sometimes its predecessor)
DataData LinkLink
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Introduction to Linked ListIntroduction to Linked List How to define the linked list data strcture in ‘C’How to define the linked list data strcture in ‘C’
struct linklist
{
int data;
struct linklist *link;
}
DataData LinkLink
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Introduction to Linked ListIntroduction to Linked List
The entire linked list is accessed from an external pointer list that points to first node in the list
The link field of the last node in the list contains a special value, known as NULLNULL
The NULL NULL pointer is used to signal the end of a list
‘‘S’S’ 4545 ‘‘O’O’ 2222 ‘‘NN’’
9999 ‘‘U’U’ NULLNULL
45 22 99
list
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Introduction to Linked ListIntroduction to Linked List
The list with no nodes on it is called the The list with no nodes on it is called the empty list or the or the null list
A list can be initialized to the empty list by list = NULLA list can be initialized to the empty list by list = NULL
Need way to indicate end of list (NULL pointer)Need way to indicate end of list (NULL pointer)
Need to know where list starts (first element)Need to know where list starts (first element)
Each element needs pointer to next element (its link)Each element needs pointer to next element (its link)
Need way to allocate new element (use malloc)Need way to allocate new element (use malloc)
Need way to return element not needed any more (use free)Need way to return element not needed any more (use free)
Divide element into data and pointerDivide element into data and pointer
‘‘S’S’ 4545 ‘‘O’O’ 2222 ‘‘NN’’
9999 ‘‘U’U’ NULLNULL
45 22 99
list
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Types of Linked List Types of Linked List
There are 4 different kinds of linked lists:There are 4 different kinds of linked lists:Linear singly linked listLinear singly linked list
Circular singly linked listCircular singly linked list
Two way or doubly linked listTwo way or doubly linked list
Circular doubly linked list.Circular doubly linked list.
‘‘S’S’ 4545 ‘‘O’O’ 2222 ‘‘NN’’
9999 ‘‘U’U’ NULLNULL
45 22 99
list
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Types of Linked List Types of Linked List
The basic operations of Linked ListThe basic operations of Linked List
Traverse Traverse
InsertInsert
At BeginningAt Beginning
At EndAt End
At given positionAt given position
DeleteDelete
At BeginningAt Beginning
At EndAt End
At given positionAt given position
UpdateUpdate
At BeginningAt Beginning
At EndAt End
At given positionAt given position
‘‘S’S’ 4545 ‘‘O’O’ 2222 ‘‘NN’’
9999 ‘‘U’U’ NULLNULL
45 22 99
list
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Sample Linked List OperationsSample Linked List OperationsStruct linklistStruct linklist
{{
int data;int data;
Struct linklist *next;Struct linklist *next;
}}
ListStart
100
ListStart
0
Pictorially In Memory
ListStart
? ? 108
100
ListStart
? ?
108Data Next
Data Next
ListStart = (linklist *) malloc(sizeof(linklist)); /* ListStart points to memory allocated at location 108 */
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Sample Linked List Operations Sample Linked List Operations (cont)(cont)
ListStart->data = 5;ListStart->data = 5;
ListStart->next = (EPtr) malloc(sizeof(EStruct));
ListStart->next = NULL;
ListStart
5 ? 108
100
ListStart
5 ?
108
ListStart
5 108
100
ListStart
5 0
108
ListStart
5 ? ? 108
100
ListStart
5 120
108
? ?
120
ListStart->next->data = 9;ListStart->next->next = NULL;
ListStart
5 9 108
100
ListStart
5 120
108
9 0
120
