DE-QueueArray.c

// DOUBLE ENDED QUEUE IMPLEMENTATION USING ARRAY

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#define CAPACITY 10

int f = -1;
int r = -1;
int queue[CAPACITY];

bool isEmpty()
{
    if (f == -1)
    {
        return true;
    }
    return false;
}

bool isFull()
{
    if (r == CAPACITY - 1)
    {
        return true;
    }
    return false;
}

void enQueueAtEnd(int data)
{

    if (isFull())
    {
        printf("Queue is Full");
        return;
    }
    if (f == -1)
    {
        f++;
    }

    queue[++r] = data;
}

void enQueueAtBeg(int data)
{

    if (isEmpty() || isFull())
    {
        enQueueAtEnd(data);
        return;
    }

    for (int i = r; i >= f; i--)
    {
        queue[i + 1] = queue[i];
    }
    r++;
    queue[f] = data;
}

void deQueueAtEnd()
{

    if (isEmpty())
    {
        printf("Queue is Empty");
        return;
    }
    r--;
}

void deQueueAtBeg()
{

    if (isEmpty())
    {
        printf("Queue is Empty");
        return;
    }
    for (int i = f + 1; i <= r; i++)
    {
        queue[i - 1] = queue[i];
    }
    r--;
}

int FrontPeek()
{

    if (isEmpty())
    {
        printf("Queue is Empty");
        exit(0);
    }
    return queue[f];
}

int RearPeek()
{

    if (isEmpty())
    {
        printf("Queue is Empty");
        exit(0);
    }
    return queue[r];
}

void printQueue()
{

    for (int i = f; i <= r; i++)
    {
        printf("%d  ", queue[i]);
    }
    printf("\n");
}

void main()
{
    enQueueAtBeg(5);
    enQueueAtEnd(15);
    enQueueAtEnd(20);
    enQueueAtBeg(25);

    printQueue();

    deQueueAtEnd();
    deQueueAtBeg();

    printQueue();

    printf("Element at first : %d\n", FrontPeek());
    printf("Element at last : %d\n", RearPeek());
}