Implementation of Priority Queue Using Linked List in C++

#include<bits/stdc++.h>
using namespace std;
struct Node
{
  int data;
  int priority;
  Node *next;
};

Node *front = NULL;

void insert (int data, int priority)
{

  Node *temp, *curr, *pre = NULL;

  temp = new Node;
  temp->data = data;
  temp->priority = priority;

  if (front == NULL or priority >= front->priority)
    {
      temp->next = front;
      front = temp;
    }

  else
    {
      curr = front;

      while (curr and priority <= curr->priority)
	{
	  pre = curr;
	  curr = curr->next;
	}

      temp->next = pre->next;
      pre->next = temp;
    }
}

void Delete ()
{
  if (front == NULL)
    {
      cout << "Priority Queue is underflow" << endl;
      return;
    }

  else
    {
      Node *temp;
      temp = front;

      cout << "Deleted item is " << temp->data << endl;

      front = temp->next;
      free (temp);
    }
}

void display ()
{
  if (front == NULL)
    cout << "Priority-Queue is empty" << endl;

  Node *curr = front;

  cout << "\nPriority-Queue elements are : ";

  while (curr)
    {
      cout << curr->data << " ";
      curr = curr->next;
    }

  cout << endl;

  return;
}

void peak ()
{
  cout << "Peak element is :" << front->data << endl;
}

int main ()
{
  insert (2, 9);
  insert (3, 4);
  insert (6, 8);

  display ();

  peak ();

  Delete ();
  Delete ();
  display ();

  return 0;

}