ARRAY IMPLEMENTATION OF CIRCULAR QUEUE

ARRAY IMPLEMENTATION OF CIRCULAR QUEUE

Aim

                        To write a c program using arrays for implementing circular queue data structure.

Algorithm

                        Step 1: [Include All Header Files Required]

                        Step 2: [Define the array size as 5 and declare front and rear pointers]

                        Step 3: Declare the functions isEmpty() , isFull(), enqueue(), size(),dequeue(), peek() and

 view()]

                        Step 4: [Call the functions]

                                    Choice :1  CALL enqueue()

                                    Choice :2  CALL deenqueue()

Choice :3  CALL peek()

Choice :4  CALL size()

Choice :5  CALL view()

Algorithm for isEmpty( )

                        Step 1: [Check for underflow]

                                    If ( front         -1 and rear          -1 )

                                    RETURN -1

                        Step 2: Else RETURN 0

                                    [Finish the process]

Algorithm for isFull( )

Step 1: [Check for overflow]

                                    If (= (rear+1)% qsize         front )

                                    RETURN -1

                        Step 2: Else RETURN 0

                                    [Finish the process]

Algorithm for Enqueue( )

STEP 1: If[front= =rear]

                        Initialize front=rear=0

STEP 2: else rear=(rear+1)% qsize

                         Set queue[rear] =value

                         [return]

Algorithm for Dequeue( )

STEP 1: If[front = =rear]

                   1.1: temp=queue[front]

                  1.2: Initialize front=rear=-1

STEP 2:else

                 2.1: front=(front+1)% qsize

                        [return]

Algorithm for Peek( )

STEP 1:If [front= =rear]

STEP 1.1: temp=queue[front]

                            [return]

Algorithm for Size( )

STEP 1:If [front= =rear]

                     1.1: Set f=front

                     1.2: Set count=1

STEP 2: If [front!=rear]

                      2.1: front=(front+1)%qsize

                      2.2: set count=count+1

                             [return]

Algorithm for View( )

STEP 1: If [front = =rear]

                         Write (“Queue is empty”)

STEP 2: else

                         [display elements]        

Coding:

#include<stdio.h>

#include<conio.h>

#define qsize 5

int queue[qsize],front=-1,rear=-1;

void enqueue(int value);

void dequeue();

void view();

void main()

{

            int c,data,item;

            clrscr();

            printf("\n1.ENQUEUE\n2.DEQUEUE\n3.VIEW");

            while(1)

            {

                        printf("\n\nEnter your Choice :: ");

                        scanf("%d",&c);

                        switch(c)

                        {

                                    case 1:

                                    printf("\nEnter the element::");

                                    scanf("%d",&data);

                                    enqueue(data);

                                    break;

                                    case 2:

                                    dequeue();

                                    break;

                                    case 3:

                                    printf("\n\nContents of circular queue is \t");

                                    view();

                                    break;

                                    default:

                                    printf("\nInvalid Choice......");

                                    exit(0);

                        }

            }

}

int isfull()

{

            extern int queue[],front,rear;

            if(front==(rear+1)%qsize)

                        return(1);

            else

                        return(0);

}

int isempty()

{

            extern int queue[],front,rear;

            if((front==-1)&&(rear==-1))

                        return(1);

            else

                        return(0);

}

void enqueue(int value)

{

            extern int queue[],front,rear;

            if(isfull())

            {

                        printf("\nOverflow");

                        return;

            }

            else

            {

                        if(isempty())

                                    front=rear=0;

                        else

                                    rear=(rear+1)%qsize;

                        queue[rear]=value;

            }

}

void dequeue()

{

            int value;

            extern int queue[],front,rear;

            if(isempty())

                        printf("\n\nQueue is Empty");

            else

            {

                        value=queue[front];

                        printf("\nDequeue value is %d",value);

            }

            if(front==rear)

            {

                        front=-1;

                        rear=-1;

            }

            else

                        front=(front+1)%qsize;

}

void view()

{

            extern int queue[],front,rear;

            int f;

            if(isempty())

                        printf("\nUnderflow");

            else

            {

                        printf("\nFront-->");

                        for(f=front;f!=rear;f=(f+1)%qsize)

                                    printf("%d ---> ",queue[f]);

                        printf("%d <--Rear",queue[f]);

            }

            if(isfull())

                        printf("\nQueue is full");

}

Output

1.ENQUEUE

2.DEQUEUE

3.VIEW

Enter your Choice :: 1

Enter the element::2

Enter your Choice :: 3

Contents of circular queue is

Front-->2 <--Rear

Enter your Choice :: 1

Enter the element::3

Enter your Choice :: 1

Enter the element::5

Enter your Choice :: 3

Contents of circular queue is

Front-->2 ---> 3 ---> 5 <--Rear

Enter your Choice :: 2

Dequeue value is 2

Enter your Choice :: 3

Contents of circular queue is

Front-->3 ---> 5 <--Rear

Enter your Choice :: 4

Invalid Choice......