1. Data Structure Lecture-5
Prepared by:
Shipra Shukla
Assistant Professor
Kaziranga University

2. Doubly Link List:Node data
info: the user's data
next, prev: the address of the next and previous node in the list
.prev
.data
. next
next
prev

3. Syntax of node
struct node { int data; struct node *next; struct node *prev; };

4. insert_at_begin
void insert_at_begin(int item) { node *ptr; ptr=(node*)malloc (sizeof(node)); ptr->info=item; if( head==(node*)null) ptr->prev=ptr->next=(node*)null; head=tail=ptr; } else ptr->prev=(node*)null; ptr->next=head; head->prev=ptr; head=ptr;

5. insert_at_end void insert_at_end(int item) { node *ptr;
ptr=(node*)malloc (sizeof(node));
ptr->info=item;
if( tail==(node*)null)
ptr->prev=ptr->next=(node*)null;
head=tail=ptr; }
else
ptr->next=(node*)null;
ptr->prev=tail;
tail->next=ptr;
tail=ptr;

6. Delete_at_begin
void delete_at_begin() { node *ptr; if( head==(node*)nulll) return; else if(head->next==(node*)null) ptr=head; head=tail=(node*)null; } else head=head->next; head->prev=(node*)null; free(ptr);

7. Delete_at_end void delete_at_end() { node *ptr;
if( tail==(node*)nulll)
return;
else if(tail->prev==(node*)null)
ptr=tail;
head=tail=(node*)null; }
else
tail=tail-> prev;
tail->next=(node*)null;
free(ptr);

8. Create Circular Doubly Linked list
node* create_list() { node* head; head=allocate_node(); head->left= head->right=head; return (head); }

9. Insert a node in a Circular Doubly Linked list
insert_cir(node*head, item) { node*ptr,*temp; int item; ptr=(node*) malloc (sizeof(node)); ptr->info=item; temp=head->right; head->right=ptr; ptr->left=head; ptr->right=temp; temp->left=ptr; return(head); }

10. Insert a node at end in a Circular Doubly Linked list
insert_cir(node*head) {
node*ptr,*temp;
int item;
ptr=(node*) malloc (sizeof(node));
ptr->info=item;
temp=head->left;
temp->right=ptr;
ptr->left=temp;
ptr->right=head;
head->left=ptr;
return(head); }

11. Delete a node at begin in a Circular Doubly Linked list
del_beg(node*head) { node*temp; if(head->right==head) printf(“List is empty”); return; } else temp=head->right; printf(“deleted element is=%d”,temp->info); head->right=temp->right; temp->right=temp->left=head; free(temp); return(head);

12. Delete a node at end in a Circular Doubly Linked list
del_end(node*head) {
node*temp;
if(head->right==head)
printf(“List is empty”);
return; }
else
temp=head->left;
printf(“deleted element is=%d”,temp->info);
head->left=temp->left;
free(temp);
return(head);