![ In array(or lists) are simple data structures used to hold sequence
of data.
Array elements are stored in consecutive memory locations. To
occupy the adjacent space, block of memory that is required for
the array should be allocated before hand.
Once memory allocated it cannot be extended any more. So that
array is called the static data structure.
Wastage of memory is more in arrays.
int a[ ]= {50,42,85,71,99};](https://image.slidesharecdn.com/unit-iidsc-160425105302/85/Unit-ii-dsc-2-320.jpg)
Unit ii(dsc++)
- 1. UNIT-IIUNIT-II Topics to be coveredTopics to be covered Singly linked listSingly linked list Circular linked listCircular linked list Doubly linked listDoubly linked list Representing Stack with linked listRepresenting Stack with linked list Representing Queues with linked listRepresenting Queues with linked list
- 2. In array(or lists) are simple data structures used to hold sequence of data. Array elements are stored in consecutive memory locations. To occupy the adjacent space, block of memory that is required for the array should be allocated before hand. Once memory allocated it cannot be extended any more. So that array is called the static data structure. Wastage of memory is more in arrays. int a[ ]= {50,42,85,71,99};
- 3. What’s wrong with Array and Why linked lists? Disadvantages of arrays as storage data structures: – slow searching in unordered array – insertion and deletion operations are slow. Because, we have to shift subsequent elements – Fixed size – Wastage of memory Linked lists solve some of these problems - Linked list is able to grow in size as needed • Does not require the shifting of items during insertions and deletions. - No wastage of memory.
- 5. Linked list Linked list is a linear data structure that supports the dynamic memory allocation( the amount of memory could be varied during its use). It is also dynamic data structure. Linked list is used to hold sequence of data values. Data values need not be stored in adjacent memory cells each data values has pointer which indicates where its next data value in computer memory. An element in a linked list is known as a node. A node contains a data part and one or two pointer part which contains the address of the neighborhood nodes in the list. Node structure-
- 7. • Types of linked list • Depending on the requirements the pointers are maintained, and accordingly linked list can be classified into three groups 1. Singly linked lists 2. Circular linked lists 3. Doubly linked lists 1. Singly linked list in singly linked list, each node has two parts one is data part and other is address part. - data part stores the data values. - address part contains the address of its next node.
- 8. • Structure of singly linked list 10 2500 2000 20 2600 2500 30 2367 40 NULL 23672600 2000 Header A NULL pointer used to mark the end of the linked list The head or header always points to the first node in the list.
- 9. Possible operations on singly linked list 1. Insertion 2. Deletion 3. Traversedisplay 4. Search 5. reverse a linked list 6. Copying 7. Merging (combine two linked lists)
- 10. Insertion in linked list • There are various positions where node can be inserted. 1. Insert at front ( as a first element) 2. Insert at end ( as a last node) 3. Insert at middle ( any position)
- 11. Singly linked lists Node Structure struct node { int data; struct node *link; }*new, *ptr, *header, *ptr1; Creating a node new = malloc (sizeof(struct node)); new -> data = 10; new -> link = NULL; data link 2000 10 new 2000 NULL
- 12. 1000 header 10 20 30 5 2000 2 1 1. Insert new node at front in linked list Algorithm step1- create a new node Step2- new->link=header->link Step3- new->data=item Step4- header->link=new. Step5-stop 5 New node 2000 1000 1500 2050 1500 2050 1000 2000
- 13. Insert new node at end of the linked list • Algorithm • Step1- create a new node • Step2- ptr=header • Step3- while(ptr->link!=null) • 3.1. ptr=ptr->link • Step4- ptr->link=new • Step5- new->data=item • Step6- new->link=null • Step7-stop
- 14. Insert new node at end of the linked list 2300 header 10 20 30 40 2500 ptr 1 2300 2400 2400 2450 2450 New 2500 Algorithm Step1- create a new node Step2- ptr=header Step3- while(ptr->link!=null) 3.1. ptr=ptr->link Step4- ptr->link=new Step5- new->data=item Step6- new->link=null Step7-stop
- 15. Insert new node at any position in linked list• Algorithm 1.Create new node 2. ptr=header 3. Enter the position 4. for(i=1;i<pos-1;i++) 4.1 ptr=ptr->link; 5. new->link=ptr->link; 6. ptr->link=new; 7. new->data=item 8.stop 10 2500 2000 20 2600 2500 30 2367 40 NULL 23672600 2000 Header Inserted position is : 3 ptr 5 New node 2600 1000
- 16. Deletion of a node from singly linked list Like insertion, there are also various cases of deletion: 1. Deletion at the front 2. Deletion at the end 3. Deletion at any position in the list
- 17. Deleting a node at the beginning if (header = = NULL) print “List is Empty”; else { ptr = header; header = header -> link; free(ptr); } 10 1800 20 30 1400 40 NULL 1500 1800 1200 1400 1200 1500 header 1500 ptr 1800
- 18. Deleting a node at the end 10 1800 20 1200 30 1400 40 NULL 1500 1800 1200 1400 1500 header ptr = header; while(ptr -> link != NULL) { ptr1=ptr; ptr = ptr -> link; } ptr1 -> link = NULL; free(ptr); 1500 ptr 18001200 NULL ptr1 ptr1 ptr1 1400
- 19. Deleting a node at the given position 10 1800 20 1200 30 1400 40 NULL 1500 header ptr = header ; for(i=1;i<pos-1;i++) ptr = ptr -> link; ptr1 = ptr -> link; ptr -> link = ptr1-> link; free(ptr1); 1500 ptr 1500 1800 1200 1400 Delete position : 31800 ptr1 1200 1400
- 20. Traversing an elements of a list 10 1800 20 1200 30 1400 40 NULL 1500 1800 1200 1400 1500 header if(header = = NULL) print “List is empty”; else for (ptr = header ; ptr != NULL ; ptr = ptr -> link) print “ptr->data”; ptr 1500
- 21. SLL program #include<stdio.h> #include<malloc.h> void search(); void traverse(); void deletion(); void insertion(); int choice,i,pos,item; struct node { int data; struct node *link; }*header,*ptr,*ptr1,*new; void main(){ header=NULL; printf("****Menu****n"); printf("n1.insertionn 2.deletionn 3.traverse n4.search n5.exitn"); while(1) { printf("nenter ur choice"); scanf("%d",&choice); switch(choice){ case 1: insertion(); break; case 2: deletion(); break; case 3: traverse(); break; case 4:search(); break; case 5:exit(0); default:printf("nwrong choicen"); }//switch}//while}//main
- 22. //insertion function void insertion() { new=malloc(sizeof(struct node)); printf("n enter the item to be insertedn"); scanf("%d",&item); new->data=item; if(header==NULL) { new->link=NULL; header=new; }//if else { printf("nenter the place to insert the itemn"); printf("1.startn 2.middlen 3. endn"); scanf("%d",&choice); if(choice==1) { new->link=header; header=new; }//if if(choice==2) { ptr=header; printf("enter the position to place itemn"); scanf("%d",&pos); for(i=0;i<pos-1;i++) ptr=ptr->link; new->link=ptr->link; ptr->link=new; }//if if(choice==3) { ptr=header; while(ptr->link!=NULL) ptr=ptr->link; new->link=NULL; ptr->link=new; }//if}//else}//insertion
- 23. //deletion function void deletion() { ptr=header; if(header==NULL) { printf("nthe list is empty"); } else { printf("n1.start n2.middle n3.end"); printf("n enter the place to delete the element from list"); scanf("%d",&choice); if(choice==1) { printf("nthe deleted item from the list is -> %d",ptr->data); header=header->link; }//if if(choice==2){ printf("n enter the position to delete the element from the list"); scanf("%d",&pos); for(i=0;i<pos-1;i++) {ptr1=ptr; ptr=ptr->link; } printf("n the deleted element is -> %d",ptr->data); ptr1->link=ptr->link; }//if if(choice==3){ while(ptr->link!=NULL){ ptr1=ptr; ptr=ptr->link; }//while printf("nthe deleted element from the list is ->%d", ptr->data); ptr1->link=NULL; }}}
- 24. void search() { int loc=0; ptr=header; printf("n enter the element to be searched in the list"); scanf("%d",&item); while((ptr->data!=item)&&(ptr- >link!=NULL)) { ptr=ptr->link; loc++; } If((ptr->link==NULL)&&(ptr- >data!=item)) Printf(“n element not found”); else printf("n the element found at location %d",loc); }//search() //traverse function void traverse() { if(header==NULL) printf("list is emptyn"); else { printf("n the elements in the list are"); for(ptr=header;ptr!=NULL;ptr=ptr->link) printf(“ %d”, ptr->data); }//else }//traverse
- 25. Disadvantage of using an array to implement a stack or queue is the wastage of space. Implementing stacks as linked lists provides a feasibility on the number of nodes by dynamically growing stacks, as a linked list is a dynamic data structure. The stack can grow or shrink as the program demands it to. A variable top always points to top element of the stack. top = NULL specifies stack is empty. Representing Stack with Linked List
- 26. In this representation, first node in the list is last inserted element hence top must points to the first element on the stack Last node in the list is the first inserted element in the stack. Thus, push operation always adds the new element at front of the list And pop operation removes the element at front of the list. Size of the stack not required. Test for overflow is not applicable in this case.
- 27. 10 NULL 1500 1800 1200 1400 20 1400 30 1200 40 1800 50 1500 1100 top Example: The following list consists of five cells, each of which holds a data object and a link to another cell. A variable, top, holds the address of the first cell in the list.
- 28. /* write a c program to implement stack using linked list */ #include<stdio.h> #include<malloc.h> #include<stdlib.h> int push(); int pop(); int display(); int choice,i,item; struct node { int data; struct node *link; }*top,*new,*ptr; main() { top=NULL; printf("n***Select Menu***n"); while(1) { printf("n1.Push n2.Pop n3.Display n4.Exitn5.Count"); printf("nnEnter ur choice: "); scanf("%d",&choice); switch(choice) { case 1: push(); break; case 2: pop(); break; case 3: display(); break; case 4: exit(0); case 5: count(); break; default: printf("nWrong choice"); }/* end of switch */ }/* end of while */ }/* end of main */
- 29. int push() { new=malloc(sizeof(struct node)); printf("nEnter the item: "); scanf("%d",&item); new->data=item; if(top==NULL) { new->link=NULL; } else { new->link=top; } top=new; return; }/* end of insertion */ int pop() { if(top = = NULL) { printf("nnStack is empty"); return; }//if else { printf("nnThe deleted element is: %d",top->data); top=top->link; } return; }/* end of pop() */
- 30. int display() { ptr=top; if(top= =NULL) { printf("nThe list is empty"); return; } printf("nThe elements in the stact are: "); while(ptr!=NULL) { printf("n %d",ptr->data); ptr=ptr->link; }/* end of while */ return; }/* end of display() */ int count() { int count=1; ptr=top; if(top = = NULL) { printf("nThe list is empty"); return; } while(ptr->link!=NULL) { ++count; ptr=ptr->link; } printf("nnThe number of elements in the stack are: %d",count); return; }/* end of count */
- 31. New items are added to the end of the list. Removing an item from the queue will be done from the front. A pictorial representation of a queue being implemented as a linked list is given below. The variables front points to the first item in the queue and rear points to the last item in the queue. Representing Queue with Linked List 10 1800 20 1200 30 1400 40 NULL 1500 1800 1200 1400 front rear
- 32. 10 1800 20 1200 30 1400 40 NULL 1500 1800 1200 1400 front rear int enqueue() {new=malloc(sizeof(struct node)); printf("nenter the item"); scanf("%d",&item); new->data=item; new->link=NULL; if(front==NULL) { front=new; } else { rear->link=new; } rear=new; return; }/*end of enqueue */
- 33. /*write a c program to implement queue using linked list*/ #include<stdio.h> #include<malloc.h> #include<stdlib.h> int choice,i,item; struct node { int data; struct node *link; }*front,*rear,*new,*ptr; main() { front=NULL; rear=NULL; printf("nn MENU"); printf("n1.Enqueue n2.Dequeue n3.Display n4.Exit"); while(1) { printf("nEnter your choice: "); scanf("%d",&choice); switch(choice) { case 1:enqueue(); break; case 2:dequeue(); break; case 3:display(); break; case 4:exit(0); default:printf("nwrong choice"); }/*end of switch */ }/*end of while */ }/*end of main */
- 34. int enqueue() { new=malloc(sizeof(struct node)); printf("nenter the item"); scanf("%d",&item); new->data=item; new->link=NULL; if(front==NULL) { front=new; } else { rear->link=new; } rear=new; return; }/*end of enqueue */ display() { if(front==NULL) printf("nThe list is emtpy"); else { for(ptr=front;ptr!=NULL;ptr=ptr->link) printf(" %d",ptr->data); } return; }/* end of display */
- 35. dequeue() { if(front==NULL) printf("nThe list is empty"); else if(front==rear) /*list has single element*/ { printf("nThe deleted element is: %d",front- >data); front=rear=NULL; } else { printf("nThe deleted element is: %d",front- >data); front=front->link; } return; }/*end ofdequeue*/
- 36. Doubly linked list In a singly linked list one can move from the header node to any node in one direction only (left-right). A doubly linked list is a two-way list because one can move in either direction. That is, either from left to right or from right to left. It maintains two links or pointer. Hence it is called as doubly linked list. Where, DATA field - stores the element or data, PREV- contains the address of its previous node, NEXT- contains the address of its next node. PREV DATA NEXT Structure of the node
- 37. Operations on doubly linked list • All the operations as mentioned for the singly linked can be implemented on the doubly linked list more efficiently. • Insertion • Deletion • Traverse • Search. Insertion on doubly linked list • Insertion of a node at the front • Insertion of a node at any position in the list • Insertion of a node at the end Deletion on doubly linked list • Deletion at front • Deletion at any position • Deletion at end
- 38. if(header==NULL) { new->prev=NULL; new->next=NULL; header=new; } else { new->next=ptr; ptr->prev=new; new->prev=NULL; header=new; } New 1200 1000 1050 2 1050 1050 1100 2000 1100 2000 1100 header ptr 1 1200 10 20 30 5 Insertion of a node at the front 1200
- 39. Insertion of a node at the end 1. Create a new node 2. Read the item 3. new->data=item 4. ptr= header 5. while(ptr->next!=NULL) 5.1 ptr=ptr->next; 6. new->next=NULL; 7. ptr->next=new; 8. new->prev=ptr; 1050 1050 1050 1100 2000 1100 2000 1100 header ptr 10 20 30 New 1200 40 1200 2000
- 40. Insertion of a node at any position in the list 1. create a node new 2. read item 3. new->data=item 4. ptr=header; 5. Read the position where the element is to be inserted 6. for(i=1;i<pos-1;i++) 6.1 ptr=ptr->next; 7. 1 ptr1=ptr->next; 7.2 new->next=ptr1; 7.3 ptr1->prev=new; 7.4 new->prev=ptr; 7.5 ptr->next=new; Algorithm
- 41. header 20 10001010 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 ptr1010 ptr 50 NULLNULL 2200 new Before inserting a node at position 3 header 20 22001010 30 20002200 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 ptr2020 ptr 50 10002020 2200 new ptr1000 ptr1 After inserting a node at position 3
- 42. Algorithm: 1.ptr=header 2.ptr1=ptr->next; 3.header=ptr1; 4.if(ptr1!=NULL) 1.ptr1->prev=NULL; 5. free(ptr); header 20 10001010 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 ptr1ptr 20 1000NULL 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 2020 1010 header Before deleting a node at beginning After deleting a node at beginning
- 43. header 20 10001010 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 Algorithm: 1. ptr=header 2. while(ptr->next!=NULL) 1. ptr=ptr->next; 3. end while 4. ptr1=ptr->prev; 5. ptr1->next=NULL; Before deleting a node at end ptrpt1header 20 10001010 30 NULL2020 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 20001000After deleting a node at end
- 44. Deletion at any position Algorithm 1. ptr=header 1.for(i=0;i<pos-1;i++) 1. ptr=ptr->next; 2. ptr1=ptr->prev; 3. ptr2=ptr->next; 4. ptr1->next=ptr2; 5. ptr2->prev=ptr1; 6. free(ptr);
- 45. header 20 10001010 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 1010 ptr1010 ptr Before deleting a node at position 3 After deleting a node at position 3 2000header 20 20001010 30 20002200 40 NULL202010 2020NULL 1010 2020 1000 2000 1010 ptr2020 ptr 1 ptr1000 ptr2
- 46. Displaying elements of a list Algorithm: 1. ptr=header; 2. if(header = = NULL) 1. printf("The list is emptyn"); 3. else 1. print “The elements in farword order: “ 2. while(ptr!=NULL) 1. print “ptr->data”; 2. if(ptr->next = = NULL) 1. break; 3. ptr=ptr->next; 3. print “The elements in reverse order: “ 4. while(ptr!=header) 4.1 print “ptr->data”; 4.2ptr=ptr->prev; 5. End while 6. print “ptr->data”; 7.end else
- 47. 20 10001010 30 20002020 40 NULL100010 2020NULL 1010 2020 1000 2000 header 1010 ptr 1010 Forward Order : 10 20 30 40 Reverse Order : 40 30 20 10
- 48. Circular linked list • In a single linked list the last node link is NULL, but a number of advantages can be gained if we utilize this link field to store the pointer of the header node.(address of first node). • Definition- the linked list where the last node points the header node is called circular linked list. Structure of the circular linked list
- 49. Advantages of circular linked list 1. Accessibility of a member node in the list 2. No Null link problem 3. Merging and splitting operations implemented easily 4. Saves time when you want to go from last node to first node. Disadvantage 1. Goes into infinite loop, if proper care is not taken 2. It is not easy to reverse the elements 3. Visiting previous node is also difficult
- 50. /* Write a c program to implement circular linked list*/ #include<stdio.h> #include<conio.h> #include<malloc.h> #include<stdlib.h> int choice,i,item; struct node { int data; struct node *link; }*front,*rear,*new,*ptr1,*ptr; main() { front=rear=NULL; printf("n select menun"); while(1) { printf("n1.Enqueue n2.Dequeue n3.Display n4.Exit"); printf("nEnter ur choice: "); scanf("%d",&choice); switch(choice) { case 1: enqueue(); break; case 2: dequeue(); break; case 3: display(); break; case 4: exit(0); default: printf("nWrong choice."); }/*end of switch*/ }/*end of while*/ }/*end of main*/
- 51. int enqueue() { new=malloc(sizeof(struct node)); printf("nEnter the item: "); scanf("%d",&item); new->data=item; if(front==NULL) front=new; else rear->link=new; rear=new; rear->link=front; return; }/*end of enqueue()*/ dequeue() { if(front==NULL) printf("nThe circular list is empty."); else if(front==rear)// cll has single element { printf("nThe deleted element is: %d",front->data) front=rear=NULL; } else { printf("nThe deleted element is: %d",front->data) front=front->link; rear->link=front; } return; }/*end of dequeue*/
- 52. display() { ptr=front; if(front==NULL) printf("nThe circular list is empty."); else { printf("nElements in the list are: "); while(ptr!=rear) { printf(" %d",ptr->data); ptr=ptr->link; }/*end of while*/ printf(“ %d”, ptr->data); return; }/*end of else*/ }/*end of display*/