#include <iostream>
using namespace std;
typedef int entrytype;
class node
{
public:
 entrytype nodedata;
 node *next;
 node()
 {
 }
 node(entrytype nodedata, node *next = nullptr)
 {
 this->nodedata = nodedata;
 this->next = next;
 }
};
class queue
{
private:
 node *first;
 node *last;
 int Size;
public:
 // constructor
 queue()
 {
 first = last = nullptr;
 Size = 0;
 }
 // destructor
 ~queue()
 {
 node *curr = first;
 // iterate over the list and delete the nodes
 while (curr != nullptr)
 {
 node *toDel = curr;
 curr = curr->next;
 delete toDel;
 }
 first = last = nullptr; // set the first AND LAST as null
 Size = 0; // set the size to zero
 }
 // method to append a node to the end of the queue
 bool append(entrytype value)
 {
 node *newNode = new node(value);
 // return false in case of overflow
 if (newNode == nullptr)
 {
 return false;
 }
 // if there is no node in the list
 if (first == nullptr)
 {
 first = newNode; // make this the head node
 last = first; // this is also the last node
 }
 // if there is atleast one node in the list
 // add it to the end of the list and update the tail
 else
 {
 last->next = newNode;
 last = last->next;
 }
 // update the size
 Size++;
 return true;
 }
 // method to access the front element of the queue
 bool front(entrytype &value)
 {
 // if queue is empty : return the underflow error
 if (first == nullptr)
 {
 return false;
 }
 // else set the value as first element's value
 value = first->nodedata;
 return true;
 }
 // method to delete the first element of the queue
 bool pop()
 {
 // if queue is empty : return underflow error code
 if (first == nullptr)
 {
 return false;
 }
 // else remove the first element of the queue
 node *toPop = first; // access the first element
 // move first to next node
 first = first->next;
 // if first became null : it means there was a single node in the list
 // so make last null as well.
 if (!first)
 last = nullptr;
 delete toPop; // delete the first node
 // update the Size
 Size--;
 return true; // return true if operation was successful
 }
 // method to get the current size of the queue
 int size()
 {
 return Size;
 }
 // method to check if given element exists in the queue
 bool find(entrytype target)
 {
 for (node *curr = first; curr != nullptr; curr = curr->next)
 {
 if (curr->nodedata == target) // if value is found return true
 return true;
 }
 return false; // return false
 }
};
int main()
{
 queue *q = new queue; // create a new queue
 // add the even elements to the queue
 for (entrytype x = 8; x <= 398; x += 2)
 {
 q->append(x);
 }
 entrytype frontEl; // to store the front of the queue
 // get the front of the queue
 q->front(frontEl);
 cout << "Front of the queue: " << frontEl << endl;
 // remove the first two elements of the queue
 cout << "Popped 2 elements from the queue\n";
 q->pop();
 q->pop();
 // check if 8 exists in the queue
 cout << "Does 8 exists in the queue? " << q->find(8) << endl;
 // check if 200 exists in the queue
 cout << "Does 200 exists in the queue? " << q->find(200) << endl;
 // report the size of the queue
 cout << "Current size of the queue: " << q->size() << endl;
 // remove 10 elements from the queue
 for (int i = 0; i < 10; i++)
 q->pop();
 cout << "Popped 10 elements from the queue\n";
 // get the new size of the queue
 cout << "Updated size of the queue: " << q->size() << endl;
 // get the front of the queue
 q->front(frontEl);
 cout << "Front of the queue: " << frontEl << endl;
 return 0;
}