UNIT 1

Data Structures Using CLinked List

ByRohit Khokher

Department of Computer Science, Vidya College of Engineering, Meerut, India

UNIT 1

LINKED LIST

A Linked List is a linear collection of data elements called nodes, where the linear order is given by means of pointers.

The each node is divided into two parts: the first part contain the information of the element, and the second part, called the link field contains the address of t he next node in the list.

x

START

LINK LIST WITH 4 NODES

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The pointer of the last node contains a special value called a null pointer which is any invalid address.

The value of null character is either ’0’ or ‘any negative value’.

The linked list also contains a list pointer variable called start which contains the address of the first node of the link list.

A special case in a list is that has no node such that list is called a null or empty list and it is represented by the null pointer in the start.

Example:- create a link list for marks of five subject 89,75,78,80,74 in ascending order

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89

75

78

80

74

5

START

2

3

4

1

0

LINK LIST REPRESENTATION OF THE

MARKS

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ALGORITHM FOR TRAVERSING A LINKED LIST

1. Set PTR=START [Initializes pointer PTR]

2. Repeat steps 3 & 4 while PTR != NULL

3. Apply process to INFO[PTR]

4. Set PTR:- LINK[PTR] [PTR now points to next node] [End of step 2 loop] 5. Exit

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PTR

PTR=LINK[PTR]

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ALGORITHM FOR SEARCHING IN A UNSORTED LINKED LIST

SEARCH(INFO,LINK,START,ITEM,LOC)

1. SET PTR = START

2. REPEAT STEP 3 WHILE PTR != NULL

3. IF ITEM = INFO[PTR] then SET LOC = PTR

& EXIT ELSE

SET PTR= LINK[PTR] [PTR now points to the next node] [END OF IF STRUCTURE]

[END OF STEP 2 LOOP]

4. [SEARCH IS UNSUCESSFUL] SET LOC=NULL

5. EXIT

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ALGORITHM FOR SEARCHING IN SORTED LIST

SRCHSL(INFO,LINK,START,ITEM,LOC)1. SET PTR = START2. REPEAT STEP 3 WHILE PTR != NULL3. IF ITEM < INFO[PTR] then;

SET PTR = LINK[PTR] [PTR now points to the next node]

ELSE IF ITEM = INFO [PTR] then;

SET LOC = PTR & EXIT [search is successful] ELSE

SET LOC = NULL & EXIT [item now exceed INFO[PTR]] [END OF IF STRUCTURE] [END OF STEP 2 LOOP]

4. [SEARCH IS UNSUCESSFUL] SET LOC=NULL5. EXIT

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OVERFLOW & UNDERFLOW CONDITIONS

OVERFLOW will occur with our link list when AVAIL= NULL &there is an insertion UNDERFLOW will occur with our link list when START=NULL & there is a deletion.

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INSERTION IN A LINKED LIST

This Can Be Done In Three Ways:

1. Beginning of the list

2. Between two nodes

3. In a sorted list

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AT BEGINNING OF THE LINKED LIST

x

START

x

AVAIL

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x

START

x

AVAIL

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ALGORITHM FOR INSERTION AT BEGINNING

INSFIRST(INFO,LINK,START,AVAIL,ITEM)

1. [OVERFLOW] if AVAIL=NULL, then write OVERFLOW & EXIT2. [ Remove first node from AVAIL list]

set NEW = AVAIL & AVAIL= LINK[AVAIL]3. Set INFO[NEW]=ITEM [copies new data into new node]4. Set LINK[NEW]= START [new node points to original first node]5. Set START= NEW [changes START so it points to the new

node]6. exit

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INSERT AFTER A GIVEN NODE

x

START

x

AVAIL

Node A Node B

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x

START

x

AVAIL

Node A Node B

Node N

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ALGORITHM FOR INSERTION AT POSITION

INSLOC(INFO,LINK,START,AVAIL,LOC,ITEM)

1. [OVERFLOW] if AVAIL=NULL, then write OVERFLOW & EXIT2. [ Remove first node from AVAIL list]

set NEW = AVAIL & AVAIL= LINK[AVAIL]3. Set INFO[NEW]=ITEM [copies new data into new node]4. If LOC=NULL then [INSERT AS A FIRST NODE]

set LINK[NEW]= START & START=NEW

else [INSERT node after node with location LOC]set LINK[NEW]=LINK[LOC] &

LINK[LOC]=NEW;[END OF IF

STRUCTURE]5. exit

UNIT 1

CREATION OF LINKED LIST

#include<stdio.h>#include<conio.h>#include<malloc.h>void main(){struct node{int num;struct node *ptr;};typedef struct node NODE;NODE *head, *first, *temp;int count=0;int choice=1;first=NULL;while(choice){

head=(NODE *)malloc(sizeof(NODE));printf("Enter the data item\n");scanf("%d",&head->num); if(first!=NULL)

{ temp->ptr=head; temp=head;}

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else{ first=temp=head;}

fflush(stdin);printf("Do you want to continue(type 0 or 1)?\n");scanf("%d",&choice);}

temp->ptr=NULL;temp=first;printf("Status of the linked list is\n");while(temp!=NULL)

{printf("%d",temp->num);count++;temp=temp->ptr;

}printf("NULL");printf("NO of nodes in the list =%d\n",count);getch();}

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Output of the Program

Enter the data item1Do you want to continue(type 0 or 1)?1Enter the data item2Do you want to continue(type 0 or 1)?1Enter the data item3Do you want to continue(type 0 or 1)?1Enter the data item4Do you want to continue(type 0 or 1)?0Status of the linked list is

1234NULLNO of nodes in the list =4

UNIT 1

Insertion in Linked List

#include<stdio.h>#include<conio.h>#include<malloc.h>struct node{int info;struct node *next;};typedef struct node NODE;NODE *start;void createmptylist(NODE *start){*start=(NODE *)NULL;}void traversinorder(NODE *start){while(start != (NODE *) NULL){printf("%d\n",start->info);start=start->next;}}

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void insertatbegin(int item){NODE *ptr;ptr=(NODE *)malloc(sizeof(NODE));ptr->info=item;if(start==(NODE *)NULL)ptr->next=(NODE *)NULL;elseptr->next=start;start=ptr;}void insert_at_end(int item){NODE *ptr,*loc;ptr=(NODE *)malloc(sizeof(NODE));ptr->info=item;ptr->next=(NODE *)NULL;if(start==(NODE*)NULL)start=ptr;

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else{loc=start;while(loc->next!=(NODE *)NULL)loc=loc->next;loc->next=ptr;}}void insert_spe(NODE *start,int item){NODE *ptr,*loc;int temp,k;for(k=0,loc=start;k<temp;k++){loc=loc->next;if(loc==NULL){printf("node in the list at less than one\n");return;}}

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ptr=(NODE *)malloc(sizeof(NODE));ptr->info=item;ptr->next=loc->next;;loc->next=ptr;}void main(){int choice,item,after;char ch;clrscr();createmptylist(start);do{printf("1.Insert element at begin \n");printf("2. insert element at end positon\n");printf("3. insert specific the position\n");printf("4.travers the list in order\n");printf("5. exit\n");

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printf("enter your choice\n");scanf("%d",&choice);switch(choice){case 1: printf("Enter the item\n");

scanf("%d",&item);insertatbegin(item);break;

case 2: printf("Enter the item\n");scanf("%d",&item);insert_at_end(item);break;

case 3: printf("Enter the item\n");scanf("%d",&item);insert_spe(start,item);break;

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case 4: printf("\ntravers the list\n");traversinorder(start);break;

case 5: return;}fflush(stdin);printf("do your want continous(y for yes)\n");scanf("%c",&ch);}while((ch='y')||(ch='Y'));getch();}

UNIT 1

THANKS