Implementation of Queue using Linked List

AIM:

          To write a C program to implement queue using linked list

ALGORITHM:

            Step 1: Start the program.

            Step 2: For queue insertion operation, check for queue overflow

Step 3: If R>=N then print queue overflow else increment rear pointer and insert  

            the element.

Step 4: For queue deletion operation, check for underflow of the queue.

Step 5: If F=0 then print queue underflow else delete the element and increment 

            the front pointer

Step 6: Stop the program.

PROGRAM

#include<stdio.h >

#include<conio.h >

#include<alloc.h >

struct queue

{

int data;

struct queue *next;

};

struct queue *addq(struct queue *front);

struct queue *delq(struct queue *front);

void main()

{

struct queue *front;

int reply,option,data;

clrscr();

front=NULL;

do

{

printf("\n1.addq");

printf("\n2.delq");

printf("\n3.exit");

printf("\nSelect the option");

scanf("%d",&option);

switch(option)

{

case 1 : //addq

front=addq(front);

printf("\n The element is added into the queue");

break;

case 2 : //delq

front=delq(front);

break;

case 3 : exit(0);

}

}while(1);

}

struct queue *addq(struct queue *front)

{

struct queue *c,*r;

//create new node

c=(struct queue*)malloc(sizeof(struct queue));

if(c==NULL)

{

printf("Insufficient memory");

return(front);

}

//read an insert value from console

printf("\nEnter data");

scanf("%d",&c->data);

c->next=NULL;

if(front==NULL)

{

front=c;

}

else

{

//insert new node after last node

r=front;

while(r->next!=NULL)

{

r=r->next;

}}

return(front);

}

struct queue *delq(struct queue *front)

{

struct queue *c;

if(front==NULL)

{

printf("Queue is empty");

return(front);

}

//print the content of first node

printf("Deleted data:%d",front->data);

//delete first node

c=front;

front=front->next;

free(c);

return(front);

}

OUTPUT

1.addq

2.delq

3.exit

Select the option 1

Enter data 8

1.addq

2.delq

3.exit

Select the option 1

Enter data 5

1.addq

2.delq

3.exit

Select the option 1

Enter data 9

1.addq

2.delq

3.exit

Select the option 1

Enter data 1

1.addq

2.delq

3.exit

Select the option 2

Deleted data: 8

1.addq

2.delq

3.exit

Select the option 3

RESULT: Thus a C program is written to implement queue using linked list and

                   executed successfully