C Program To Implement a Queue

// C Program to demonstrate how to Implement a queue
#include <stdbool.h>
#include <stdio.h>
#define MAX_SIZE 100

// Defining the Queue structure
typedef struct {
    int items[MAX_SIZE];
    int front;
    int rear;
} Queue;

// Function to initialize the queue
void initializeQueue(Queue* q)
{
    q->front = -1;
    q->rear = 0;
}

// Function to check if the queue is empty
bool isEmpty(Queue* q) { return (q->front == q->rear - 1); }

// Function to check if the queue is full
bool isFull(Queue* q) { return (q->rear == MAX_SIZE); }

// Function to add an element to the queue (Enqueue
// operation)
void enqueue(Queue* q, int value)
{
    if (isFull(q)) {
        printf("Queue is full\n");
        return;
    }
    q->items[q->rear] = value;
    q->rear++;
}

// Function to remove an element from the queue (Dequeue
// operation)
void dequeue(Queue* q)
{
    if (isEmpty(q)) {
        printf("Queue is empty\n");
        return;
    }
    q->front++;
}

// Function to get the element at the front of the queue
// (Peek operation)
int peek(Queue* q)
{
    if (isEmpty(q)) {
        printf("Queue is empty\n");
        return -1; // return some default value or handle
                   // error differently
    }
    return q->items[q->front + 1];
}

// Function to print the current queue
void printQueue(Queue* q)
{
    if (isEmpty(q)) {
        printf("Queue is empty\n");
        return;
    }

    printf("Current Queue: ");
    for (int i = q->front + 1; i < q->rear; i++) {
        printf("%d ", q->items[i]);
    }
    printf("\n");
}

int main()
{
    Queue q;
    initializeQueue(&q);

    // Enqueue elements
    enqueue(&q, 10);
    printQueue(&q);

    enqueue(&q, 20);
    printQueue(&q);

    enqueue(&q, 30);
    printQueue(&q);

    // Peek front element
    printf("Front element: %d\n", peek(&q));

    // Dequeue an element
    dequeue(&q);
    printQueue(&q);

    // Peek front element after dequeue
    printf("Front element after dequeue: %d\n", peek(&q));

    return 0;
}