This document presents information on doubly linked lists including their representation, initialization, node creation, and various operations like insertion, deletion, and traversal. It discusses inserting and deleting nodes at the beginning or end of the list, as well as inserting before or after a specified node. Code examples are provided for initializing a doubly linked list and performing each operation.

1. Presentation on doubly linked list:- Presented by:- RITU NAMDEO M.C.A. 2 ND SEM ‘ B’ SEC. MITM INDORE

2. Doubly linked list Doubly-linked list(DLL) is a more sophisticated kind of linked list. Each has three parts ,two links parts and one data parts. One points to previous node and one points to next node. There are two pointer variable head and tail. Head points to the first element of list and tail points last element of list.

3. REPRESENTATION OF DLL PPPP D D P D N D Head Tail

4. DLL OPERATIONS: INITIALIZING CREATING A NODE

5. Initializing Tail Head

6. Code initialization >>.. initialize(node **head,node **tail){ *head=NULL; *tail=NULL; }

7. Creating a node data ptr tail

8. Function for creating a node node* create(int item){ node *ptr; ptr=(node*)malloc(sizeof(node)); ptr->item=item; ptr->prev=NULL; ptr->next=NULL; return ptr;

9. OPERATIONS ON DLL INSERTION At beginning of list At end of list After a specified node Before a specified node Deletion At beginning of list At end of list After a specified node Before a specified node Traversing

10. Insertion at begining Check for list is empty or not. insrt_beg(node **head,node **tail,itemtype item) { node *ptr; ptr=create(item); if(*head==NULL&&*tail==NULL){ *head=ptr; *tail=ptr; } Head Tail

11. Insertion at beginning Before insertion 20 10 30 Head Tail

12. new node 2 ptr tail

13. Insertion 2 ptr tail 20 10 30 Head Tail

14. Insertion of new node 10 2 20 Head Tail 30

15. Code:- function insrt_beg(node **head,node **tail,itemtype item) { node *ptr; ptr=create(item); if(*head==NULL&&*tail==NULL){ *head=ptr; *tail=ptr; } else{ (*head)->prev=ptr; ptr->next=*head; *head=ptr; ptr==NULL; } }

16. Insert at last of list new node before insertion 40 ptr tail

17. 40 ptr tail 20 10 30 Head Tail

18. After insertion new node 20 10 30 Head Tail 40

19. Code for this operation:- insrt(node ** head,node **tail,itemtype item){ node *ptr; ptr=create(item); if(*head==NULL&& *tail==NULL){ *head=ptr; *tail=ptr; } else{ ptr->prev=*tail; (*tail)->next=ptr; *tail=ptr; ptr=NULL; } }

20. Insertion before a specified node:- new node 40 ptr tail

21. Inserting new node Inserting before 30 20 10 40 Head Tail 30

23. function insrt_bfr_specify(node **head,node **tail,itemtype item,itemtype sitem) { node *ptr,*temp,*temp1 ptr=create(item); temp=*head; if(*head==NULL&&*tail==NULL){ *head=ptr; *tail=ptr; } else{ while(temp->item!=sitem&&temp->next!=NULL) { temp=temp->next;

24. Cont. } if(temp==NULL) printf("item was not found"); else { temp1=temp->prev; ptr->prev=temp1->next; temp1->next=ptr; ptr->next=temp; temp->prev=ptr; ptr=NULL; } }

25. After a specified node New node 40 ptr tail

26. Inserting after 20: 20 10 40 Head Tail 30

27. Code :- insrt_aftr_specify(node **head,node **tail,itemtype item,itemtype sitem){ node *ptr,*temp,*temp1; ptr=create(item); temp=*head; if(*head==NULL&&*tail==NULL){ *head=ptr; *tail=ptr; } else{ while(temp->item!=sitem&&temp->next!=NULL) { temp=temp->next;

28. Cont. } if(temp==NULL) printf("item was not found"); else { temp1=temp->next; ptr->prev=temp; ptr->next=temp->next; temp1->prev=ptr; temp->next=ptr; ptr=NULL; } } }

29. Deletion in DLL Deletion at begining case :-if list is empty. Head Tail

30. function deletion_at_beg(node **head){ node *temp; temp=*head; head=temp->next; (*head)->prev=NULL; free(temp); }

31. Deleting first node 10 2 20 Head Tail 30

32. 10 20 Head Tail 30

33. Traversing 10 Head 20 30 Tail

34. fuction show(node *q) { while(q!=NULL) { printf("%d-",q->item); q=q->next; } }

35. Code: main function void main() { int item,sitem,ch; char c; node *head,*tail; clrscr(); initialize(&head,&tail); do { ch=list(); switch(ch){

36. case 1: printf("please enter the item"); scanf("%d",&item); insrt(&head,&tail,item); show(head); break;

37. case 2: printf("please enter the item"); scanf("%d",&item); insrt_beg(&head,&tail,item); show(head); break;

38. Cont. case 3: printf("please enter the item"); scanf("%d",&item); show(head); printf("please enter the specify item"); scanf("%d",&sitem); insrt_bfr_specify(&head,&tail,item,sitem); show(head); break;

39. Cont. case 4: printf("please enter the item"); scanf("%d",&item); show(head); printf("please enter the specify item"); scanf("%d",&sitem); insrt_aftr_specify(&head,&tail,item,sitem); show(head); break;

40. Cont. case 5: show(head); deletion_at_beg(&head); show(head); break; default: printf("no choice"); } printf("\n\ndo u want to continue y\n"); scanf("\n%c",&c); }while(c=='y'||c=='Y'); getch(); }

41. Display function list() { int k; printf("\nchoose 1* for insert value in the list"); printf("\nchoose 2* for insert at begiging in the list"); printf("\nchoose 3* for insert before specified node inthe list"); printf("\nchoose 4* for insert after specified node inhe list"); printf("\nchoose 5* for delete begining from the list"); scanf("\n%d",&k); return(k); }