#include <bits/stdc++.h> 
using namespace std; 
  
// A linked list (LL) node to store a queue entry 
class QNode { 
public: 
    int key; 
    QNode* next; 
}; 
  
// The queue, front stores the front node 
// of LL and rear stores the last node of LL 
class Queue { 
public: 
    QNode *front, *rear; 
}; 
  
// A utility function to create 
// a new linked list node. 
QNode* newNode(int k) 
{ 
    QNode* temp = new QNode(); 
    temp->key = k; 
    temp->next = NULL; 
    return temp; 
} 
  
// A utility function to create an empty queue 
Queue* createQueue() 
{ 
    Queue* q = new Queue(); 
    q->front = q->rear = NULL; 
    return q; 
} 
  
// The function to add a key k to q 
void enQueue(Queue* q, int k) 
{ 
    // Create a new LL node 
    QNode* temp = newNode(k); 
  
    // If queue is empty, then 
    // new node is front and rear both 
    if (q->rear == NULL) { 
        q->front = q->rear = temp; 
        return; 
    } 
  
    // Add the new node at 
    // the end of queue and change rear 
    q->rear->next = temp; 
    q->rear = temp; 
} 
  
// Function to remove 
// a key from given queue q 
QNode* deQueue(Queue* q) 
{ 
    // If queue is empty, return NULL. 
    if (q->front == NULL) 
        return NULL; 
  
    // Store previous front and 
    // move front one node ahead 
    QNode* temp = q->front; 
    delete(temp); 
  
    q->front = q->front->next; 
  
    // If front becomes NULL, then 
    // change rear also as NULL 
    if (q->front == NULL) 
        q->rear = NULL; 
    return temp; 
} 
  
// Driver code 
int main() 
{ 
    Queue* q = createQueue(); 
    enQueue(q, 10); 
    enQueue(q, 20); 
    deQueue(q); 
    deQueue(q); 
    enQueue(q, 30); 
    enQueue(q, 40); 
    enQueue(q, 50); 
    QNode* n = deQueue(q); 
    if (n != NULL) 
        cout << "Dequeued item is " << n->key; 
    return 0; 
} 
  
// This code is contributed by rathbhupendra