#include <stdio.h>
#include <stdlib.h>
 
#define SIZE 100  // Define the maximum size of the queue
 
int queue[SIZE];
int front = -1;
int rear = -1;
 
// Function to check if queue is full
int isFull() {
    return (rear == SIZE - 1);
}
 
// Function to check if queue is empty
int isEmpty() {
    return (front == -1 || front > rear);
}
 
// Function to enqueue (insert) an element
void enqueue(int value) {
    if (isFull()) {
        printf("\nQueue Overflow! Cannot insert %d\n", value);
        return;
    }
 
    if (front == -1)
        front = 0;
 
    rear++;
    queue[rear] = value;
    printf("\n%d enqueued to queue.\n", value);
}
 
// Function to dequeue (remove) an element
void dequeue() {
    if (isEmpty()) {
        printf("\nQueue Underflow! No elements to dequeue.\n");
        return;
    }
 
    printf("\n%d dequeued from queue.\n", queue[front]);
    front++;
 
    // Reset queue when all elements are removed
    if (front > rear)
        front = rear = -1;
}
 
// Function to peek (view the front element)
void peek() {
    if (isEmpty()) {
        printf("\nQueue is empty.\n");
        return;
    }
    printf("\nFront element is: %d\n", queue[front]);
}
 
// Function to display all elements
void display() {
    if (isEmpty()) {
        printf("\nQueue is empty.\n");
        return;
    }
 
    printf("\nQueue elements are:\n");
    for (int i = front; i <= rear; i++)
        printf("%d ", queue[i]);
    printf("\n");
}
 
// Main function
int main() {
    int choice, value;
 
    printf("=== QUEUE IMPLEMENTATION USING ARRAY ===\n");
 
    while (1) {
        printf("\nMenu:\n");
        printf("1. Enqueue\n");
        printf("2. Dequeue\n");
        printf("3. Peek\n");
        printf("4. Display\n");
        printf("5. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
 
        switch (choice) {
            case 1:
                printf("Enter value to enqueue: ");
                scanf("%d", &value);
                enqueue(value);
                break;
            case 2:
                dequeue();
                break;
            case 3:
                peek();
                break;
            case 4:
                display();
                break;
            case 5:
                printf("\nExiting program.\n");
                exit(0);
            default:
                printf("\nInvalid choice! Try again.\n");
        }
    }
 
    return 0;
}