Program to Implement Queue Using Array in C

/*==========================================================================================
**
**  File Name     : queue_array.c
**  Creation Date : Fri 13 Oct 2017 11:46:43 PM IST
**  Last Modified : Thu 19 Oct 2017 07:59:05 PM IST
**  Compiler      : gcc
**  Author        : Manoj Kumar Patra, Asst. Professor
**  Organization  : Vignan University, Guntur, India.
**
**=========================================================================================*/

#include<stdio.h>
#include<stdlib.h>
#define MAX 100

int queue_array[MAX];
int front=-1;
int rear=-1;

void enqueue(int item);
int dequeue();
int peek();
void display();
int isFull();
int isEmpty();

main()
{
    int choice,item;
    printf("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =\n");
    printf("= = = = = = = = = = Queue Using Array in C = = = = = = = = = =\n");
    while(1)
    {
        printf("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =\n");
        printf("1. Enqueue\n");
        printf("2. Dequeue\n");
        printf("3. Display\n");
        printf("4. Peek\n");
        printf("5. Quit\n");
        printf("\nEnter your choice : ");
        scanf("%d",&choice);

        switch(choice)
        {
        case 1:
            printf("Enter the number to be added in queue : ");
            scanf("%d",&item);
            enqueue(item);
            printf("Number %d das been added to the queue\n",item);
            break;
        case 2:
            item=dequeue();
            printf("Front element %d has been deleted\n",item);
            break;
        case 3:
            display();
            break;
        case 4:
            printf("Front element in the Queue is: %d\n",peek());
            break;
        case 5:
            printf("Program Terminated..!!\n");
            printf("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =\n\n");
            exit(1);
        default:
            printf("Oops... Wrong choice..!!\n");
        }
    }
}

// 1 ok
void enqueue(int item)
{
    if(isFull())
    {
        printf("Queue Overflow\n");
        return;
    }
    if(front == -1)
        front=0;
    rear=rear+1;
    queue_array[rear]=item ;
}

// 2 ok
int dequeue()
{
    int item;
    if(isEmpty())
    {
        printf("Queue Underflow\n");
        exit(1);
    }
    item=queue_array[front];
    front=front+1;
    return item;
}

// 3 ok

void display()
{
    int i;
    if(isEmpty())
    {
        printf("Queue is empty\n");
        return;
    }
    printf("Queue elements are :\n\n");
    for(i=front; i<=rear; i++)
        printf("%d\t",queue_array[i]);
    printf("\n\n");
}


// 4 ok

int peek()
{
    if(isEmpty())
    {
        printf("Queue Underflow\n");
        exit(1);
    }
    return queue_array[front];
}


// 5 ok

int isEmpty()
{
    if(front==-1 || front==rear+1)
        return 1;
    else
        return 0;
}

// 6 ok
int isFull()
{
    if(rear == MAX-1)
        return 1;
    else
        return 0;
}

OutPut:

manoj@ubuntu:~/ds/queue$ gcc queue_array.c -o queue_array
manoj@ubuntu:~/ds/queue$ ./queue_array
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = Queue Using Array in C = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 1
Enter the number to be added in queue : 10
Number 10 das been added to the queue
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 1
Enter the number to be added in queue : 20
Number 20 das been added to the queue
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 1
Enter the number to be added in queue : 30
Number 30 das been added to the queue
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 1
Enter the number to be added in queue : 40
Number 40 das been added to the queue
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 1
Enter the number to be added in queue : 50
Number 50 das been added to the queue
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 3
Queue elements are :

10    20    30    40    50   

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 2
Front element 10 has been deleted
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 3
Queue elements are :

20    30    40    50   

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 4
Front element in the Queue is: 20
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1. Enqueue
2. Dequeue
3. Display
4. Peek
5. Quit

Enter your choice : 5
Program Terminated..!!
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

manoj@ubuntu:~/ds/queue$