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Linked list
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- 2. What is LinkedList A linked list is a linear collection of data elements, called nodes, each pointing to the next node by means of a pointer. It is a data structure consisting of a group of nodes which together represent a sequence. Linked lists were developed in 1955–1956 by Allen Newell, Cliff Shaw and Herbert A. Simon. It contains data field & Address field or Link field.
- 3. A graphical viewof a linked list
- 4. Why do weuse Linked List? Linked lists are preferable over arrays when: a) we need constant-time insertions/deletions from the list (such as in real-time computing where time predictability is absolutely critical ) b) We don't know how many items will be in the list. With arrays, you may need to re-declare and copy memory if the array grows too big c) We don't need random access to any elements d) We want to be able to insert items in the middle of the list (such as a priority queue)
- 5. Types of LinkedList There are three types of linked list as given below: 1. Singly Linked List 2. Doubly Linked List 3. Circular Linked List
- 6. Singly Linked List Agraphical view of a singly linked list
- 7. Doubly Linked List Indoubly linked list each node is divided into three parts: 1. The first part is PREV part. 2. The second part is the INFO part. 3. The third part is NEXT part.
- 8. A graphical viewof a doubly linked list
- 9. Circular Linked List Agraphical view of a circular linked list
- 10. Singly Linked ListOperations There are several operations in singly linked list: 1.Creation 2. Insertion 3. Deletion 4. Searching 5. Display
- 11. Nodes • Nodes arethe units which makes up linked list. • In singly linked list, nodes are actually structures made up of data and a pointer to another node. • Usually we denote the pointer as “*next”
- 12. *Nodes structure struct node { intdata; //This is where we will store data struct node *next; //This is the link part }*head=NULL; /*Initially we assign “NULL” to the head for later operational purpose*/
- 13. *Visual Representation ofNode data next Node
- 14. Creation • Creation operationis used to create a linked list. • Generally, we use dynamic memory allocation to create our desired number of nodes for linked list in program run time.
- 15. void create() { struct node*newnode, *current; newnode = (struct node*)malloc(sizeof(struct node)); newnode->next = NULL; if(head == NULL) { head = newnode; current = newnode; } else { current->next = newnode; current = newnode; } } //Creating linked list in ‘C’
- 16. *Visual Representation ofLinked List data next Head data next data next NULL
- 17. Insertion • Insertion operationis used to insert a new node in the linked list. • Insertion is of three types. They are: Inserting at first Inserting at last Inserting at mid
- 18. Insertion at first •There are two steps to be followed to insert a node at first position. They are: Make the next pointer of the node point towards the first node of the list. Make the head pointer point towards this new node.
- 19. *Visual Representation ofInsertion at First data next Head data next data next NULL Newnode nextdata
- 20. void first_insert() { struct node*newnode, *current; newnode = (struct node*)malloc(sizeof(struct node)); newnode->next = NULL; if(head == NULL) { head = newnode; current = newnode; } else { newnode->next = head; head = newnode; } } //Inserting at first
- 21. Insertion at last •Inserting at the last position is a simple process. To insert at last we just simply need to make the next pointer of last node to the new node.
- 22. *Visual Representation ofInsertion at Last data next Head data next data next NULLdata next Newnode Current/ Last
- 23. void last_insert() { struct node*newnode, *current; newnode = (struct node*)malloc(sizeof(struct node)); newnode->next = NULL; if(head == NULL) { head = newnode; current = newnode; } else { current->next = newnode; current = newnode; } } //Inserting at last
- 24. Insertion at mid •There are several steps to be followed to insert a node at mid position. They are: Find the position after which and before which node the new node is going to be inserted. Assign their locations to two different pointers named ‘temp’, ‘temp2’ respectively. Make the next pointer of ‘temp’ to point newnode, and the next pointer of newnode to ‘temp2’.
- 25. *Visual Representation ofInsertion at Last data next Head data next data next NULL data next Newnode temp temp2
- 26. void mid_insert() { struct node*newnode, *temp, *temp2; int position; newnode = (struct node*)malloc(sizeof(struct node)); newnode->next = NULL; if(head == NULL) { head = newnode; current = newnode; } else { temp=head; for(i=1;i<position;i++) temp = temp->next; temp2 = temp->next; temp->next = newnode; newnode->next=temp2; } //Inserting at mid
- 27. Deletion • Deleting isa simple process. At first we need to find the previous and the next node of that particular node. Then we need to point the next pointer of the previous node to the next node of the particular node we want to delete.
- 28. *Visual Representation ofDeletion data next Head data next data next NULL temp temp2
- 29. void delete_node(int n){ inti; struct node* temp,*p; temp=root; if(n==1){ root=temp->link; } else{ for(i=1;i<n-1;i++){ temp=temp->link; } p=temp->link; temp->link=p->link; } } //Deletion
- 30. Searching • To searchin a linked list we need to follow the steps given below: We need a pointer which is assigned with the address of head pointer. Then we start a loop until the last node of the linked list to search.
- 31. int search(int n){ inti; struct node* temp; temp=root; int l=length(); for(i=1;i<=l;i++){ if(temp->data==n){ return i; } temp=temp->link; } if(i>l){ return 0; } } //Searching
- 32. Display • To displaythelinked list we need to follow the steps given below: We need a pointer which is assigned with the address of head pointer. Then we start a loop until the last node of the linked list to display the the list.
- 33. void display(){ struct node*temp; temp=root; if(temp==NULL){ printf("no data foundn"); } else{ while(temp!=NULL){ printf("%d-->>",temp->data); temp=temp->link; } } } //Display
- 34. Uses of LinkedList 1. Web-browsers A good example I see is web-browsers, where it creates a linked list of web-pages visited, so that when you check history (traversal of a list) or press back button, the previous node's data is fetched. 2. Stacks and queues It is used to develop stacks and queues which have lots of applications.
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- 36. 4. Phonebook In phonebookthe names are sorting in ascending order. If we want to add a new contact then the memory for the new contact is created by linked list.
- 37. Advantages • Linked listsare a dynamic data structure, allocating the needed memory while the program is running. • Insertion and deletion node operations are easily implemented in a linked list. • Linear data structures such as stacks and queues are easily executed with a linked list. • They can reduce access time and may expand in real time without memory overhead.
- 38. Disadvantages • They havea quite difficult to use more memory due to pointers requiring extra storage space. • Nodes in a linked list must be read in order from the beginning as linked lists are inherently sequential access. • Nodes are stored in continuously, greatly increasing the time required to access individual elements within the list. • Difficulties arise in linked lists when it comes to reverse traversing. For instance, singly linked lists are cumbersome to navigate backwards and while doubly linked lists are somewhat easier to read, memory is wasted in allocating space for a back pointer.
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