Circular Queue Using an Array

Circular Queue Using an Array

#include <stdio.h>

#include<stdlib.h>

#define MAX 3

char cq[MAX];

int front = -1,rear = -1;

void add(char);

void del();

void display();

int main()

{

            int ch;

            char item;

            while(1)

            {

                        printf("\n\n~~Main Menu~~");

                        printf("\n==> 1. Insertion and Overflow Demo");

                        printf("\n==> 2. Deletion and Underflow Demo");

                        printf("\n==> 3. Display");

                        printf("\n==> 4. Exit");

                        printf("\nEnter Your Choice: ");

                        scanf("%d", &ch);

                        switch(ch)

                        {

                                    case 1: printf("\n\nEnter the element to be inserted: ");

                                                scanf("%d", &item);

                                                add(item);

                                                break;

                                    case 2: del();

                                                break;

                                   case 3: display();

                                                break;

                                    case 4: exit(0);

                                    default: printf("\n\nPlease enter a valid choice");

                        }

            }

}

void add(char item)

{

            if(front == (rear+1)%MAX)

                        printf("\n\n~~Circular Queue Overflow~~");

            else

            {

                        if(front == -1)

                                    front = rear = 0;

                        else

                                    rear = (rear+1)%MAX;

                        cq[rear] = item;

            }

}

void del()

{

            char item;

            if(front == -1)

            {

                        printf("\n\n~~Circular Queue Underflow~~");

            }

            else

            {

                        item = cq[front];

                        if(front == rear) //only one element

                                    front = rear = -1;

                        else

                                    front = (front+1)%MAX;

                        printf("\n\nDeleted element from the queue is: %d ", item );

            }

}

void display ()

{

            int i ;

            if(front == -1)

            {

                        printf("\n\nCircular Queue Empty");

                        return;

            }

            else

            {

                        printf("\nCircular Queue contents are:\n");

                        printf("\nFront[%d]-> ", front);

                        for(i=front; i!=rear ; i=(i+1)%MAX)

                        {

                                    printf("  %d", cq[i]);

                        }

                        printf("  %d",cq[i]);

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

    }

}

Output:

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 1

Enter the element to be inserted: 11

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 1

Enter the element to be inserted: 22

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 1

Enter the element to be inserted: 33

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 1

Enter the element to be inserted: 44

~~Circular Queue Overflow~~

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 3

Circular Queue contents are:

Front[0]->   11  22  33 <-[2]Rear

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 2

Deleted element from the queue is: 11

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 2

Deleted element from the queue is: 22

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 3

Circular Queue contents are:

Front[2]->   33 <-[2]Rear

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 1

Enter the element to be inserted: 66

~~Main Menu~~

==> 1. Insertion and Overflow Demo

==> 2. Deletion and Underflow Demo

==> 3. Display

==> 4. Exit

Enter Your Choice: 3

Circular Queue contents are:

Front[2]->   33  66 <-[0]Rear