Linear Queue using an array

Linear Queue using an Array

#include<stdio.h>

#include<stdlib.h>

#define MAX 5

int front = -1;

int rear = -1;

int q[MAX];

void insert();

void delete();

void display();

void main()

{

            int ch;

            while(1)

            {

                        printf("\n\nMenu\n1.Insert\n2.Delete\n3.Display\n4.exit");

                        printf("\nEnter your choice:\t");

                        scanf("%d",&ch);

                        switch(ch)

                        {

                                    case 1:                         insert();

                                                            display();

`                                                           break;

                                    case 2:                         delete();

                                                            display();

                                                            break;

                                    case 3:                         display();

                                                            break;

                                    case 4:                         exit(0);

                                    default:            printf("\nInvalid Choice\n");

                        }

            }

}

void insert()

{

            int item;

            if(rear == MAX-1)

            {

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

                        return;

            }

            printf("\nEnter the item to to be inserted:");

            scanf("%d", &item);

            rear = rear+1;

            q[rear] = item;

}

void delete()

{

            int item;

            if(front == rear)

            {

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

                        return;

            }

            front = front+1;

            item = q[front];

            printf("\nThe item that got deleted is: %d", item);

}

void display()

{

            int i;

            printf("\nfront = %d, rear = %d",front, rear);

            if(front == rear)

            {

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

                        return;

            }

            else

            {

                        printf("\nElements of the queue are: ");

                        for(i=front+1; i<=rear;i++)

                                                            printf("%d\t",q[i]);

            }

}

Output:

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

Enter the item to to be inserted: 11

front = -1, rear = 0

Elements of the queue are: 11

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

Enter the item to to be inserted:       22

front = -1, rear = 1

Elements of the queue are: 11   22

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

Enter the item to to be inserted:         33

front = -1, rear = 2

Elements of the queue are: 11   22   33

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

Enter the item to to be inserted:       44

front = -1, rear = 3

Elements of the queue are: 11   22    33   44

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

Enter the item to to be inserted: 55

front = -1, rear = 4

Elements of the queue are: 11   22  33  44  55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      1

~~~Queue Overflow~~~

front = -1, rear = 4

Elements of the queue are: 11  22  33  44  55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

The item that got deleted is:            11

front = 0, rear = 4

Elements of the queue are: 22   33  44  55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

The item that got deleted is:             22

front = 1, rear = 4

Elements of the queue are: 33   44   55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

The item that got deleted is:             33

front = 2, rear = 4

Elements of the queue are: 44   55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

The item that got deleted is:             44

front = 3, rear = 4

Elements of the queue are: 55

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

The item that got deleted is: 55

front = 4, rear = 4

Queue is empty

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      2

~~~Queue Underflow~~~

front = 4, rear = 4

Queue is empty

Menu

1.Insert

2.Delete

3.Display

4.exit

Enter your choice:      4