Queue basic code, enqueue, dequeue

#include<iostream>
using namespace std;

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

class queue{
    node *front;
    node *rear;
public:
    queue(){
        front = rear = NULL;
    }

    bool isEmpty(){
        if(rear == NULL){
            return true;
        }
        else{
            return false;
        }
    }

    void enqueue(int v){
        node *t = new node;
        t -> data = v;
        t -> next = NULL;
        //If queue is empty, new node is front and rear both
        if(rear == NULL){
            front = t;
            rear = t;
            return;
        }
        //Add new node at end of the queue
        rear -> next = t;
        rear = t;
    }

    int dequeue(){
        if(front == NULL){
            //cout << "Queue is empty" << endl;
            return -1;
        }
        //Store previous front and move front one node ahead
        node *t = front;
        front = front -> next;
        //If front becomes NULL, change rear as NULL too
        if(front == NULL){
            rear == NULL;
        }
        int val = t -> data;
        free(t);
        return val;
    }

    void display(){
            node *t=front;
            while(t!=NULL){
                cout << t->data <<" -> ";
                t=t->next;
            }
            cout<<"NULL\n";
        }
};

int main(){
    queue q;
    int ch = 10;
    while(ch != 0){
        cout << "Enter your choice" << endl;
        cout << "1: Enqueue element" << endl;
        cout << "2: Dequeue element" << endl;
        cout << "0: Exit" << endl;
        cin >> ch;
        switch(ch){
        case 1:
            int value;
            cout << "Enter value: " << endl;
            cin >> value;
            q.enqueue(value);
            q.display();
            break;
        case 2:
            cout << "The dequeued element is: " << q.dequeue() << endl;
            q.display();
            break;
        }
    }
    return 0;
}