Day 8 of DSA in C

Write a menu driven C program to create a queue using linked list and perform basic functions on it.

        
#include <stdio.h>
#include <stdlib.h>

#define MAX 5

struct Node {
    int data;
    struct Node* next;
};

struct Node* front = NULL;
struct Node* rear = NULL;
int count = 0;

void enqueue(int value) {
    if (count == MAX) {
        printf("Queue Overflow! (limit %d)\n", MAX);
        return;
    }
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (!newNode) {
        printf("Memory allocation failed!\n");
        return;
    }
    newNode->data = value;
    newNode->next = NULL;
    if (rear == NULL) {
        front = rear = newNode;
    } else {
        rear->next = newNode;
        rear = newNode;
    }
    count++;
    printf("Enqueued %d into queue.\n", value);
}

void dequeue() {
    if (front == NULL) {
        printf("Queue Underflow!\n");
        return;
    }
    struct Node* temp = front;
    printf("Dequeued %d from queue.\n", temp->data);
    front = front->next;
    if (front == NULL) rear = NULL;
    free(temp);
    count--;
}

void display() {
    if (front == NULL) {
        printf("Queue is empty!\n");
        return;
    }
    struct Node* temp = front;
    printf("Queue elements: ");
    while (temp != NULL) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}

int main() {
    int choice, value;
    while (1) {
        printf("\n---- QUEUE MENU ----\n");
        printf("1. Enqueue\n");
        printf("2. Dequeue\n");
        printf("3. Display\n");
        printf("4. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter value: ");
                scanf("%d", &value);
                enqueue(value);
                break;
            case 2:
                dequeue();
                break;
            case 3:
                display();
                break;
            case 4:
                printf("Exiting...\n");
                exit(0);
            default:
                printf("Invalid choice! Try again.\n");
        }
    }
    return 0;
}