min heap declaration in c++ stl

// C++ program to use priority_queue to implement min heap 
#include <bits/stdc++.h> 
using namespace std; 
  
// Driver code 
int main () 
{ 
    // Creates a min heap 
    priority_queue <int, vector<int>, greater<int> > pq; 
    pq.push(5); 
    pq.push(1); 
    pq.push(10); 
    pq.push(30); 
    pq.push(20); 
  
    // One by one extract items from min heap 
    while (pq.empty() == false) 
    { 
        cout << pq.top() << " "; 
        pq.pop(); 
    } 
  
    return 0; 
} 
// C++ program to show that priority_queue is by 
// default a Max Heap 
#include <bits/stdc++.h> 
using namespace std; 
  
// Driver code 
int main () 
{ 
    // Creates a max heap 
    priority_queue <int> pq; 
    pq.push(5); 
    pq.push(1); 
    pq.push(10); 
    pq.push(30); 
    pq.push(20); 
  
    // One by one extract items from max heap 
    while (pq.empty() == false) 
    { 
        cout << pq.top() << " "; 
        pq.pop(); 
    } 
  
    return 0; 
} 
// C++ code to demonstrate the working of  
// make_heap(), front() 
#include<bits/stdc++.h>  
using namespace std; 
int main() 
{ 
      
    // Initializing a vector 
    vector<int> v1 = {20, 30, 40, 25, 15}; 
      
    // Converting vector into a heap 
    // using make_heap() 
    make_heap(v1.begin(), v1.end()); 
      
    // Displaying the maximum element of heap 
    // using front() 
    cout << "The maximum element of heap is : "; 
    cout << v1.front() << endl; 
      
    return 0; 
}