min and max heap in cpp

priority_queue <int, vector<int>, greater<int>> minHeap;

priority_queue <int> maxHeap; 

// 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; 
} 

priority_queue <int, vector<int>, greater<int>> minHeap;
priority_queue <int> maxHeap; 

#include <iostream>
using namespace std;
void max_heap(int *a, int m, int n) {
   int j, t;
   t = a[m];
   j = 2 * m;
   while (j <= n) {
      if (j < n && a[j+1] > a[j])
         j = j + 1;
      if (t > a[j])
         break;
      else if (t <= a[j]) {
         a[j / 2] = a[j];
         j = 2 * j;
      }
   }
   a[j/2] = t;
   return;
}
void build_maxheap(int *a,int n) {
   int k;
   for(k = n/2; k >= 1; k--) {
      max_heap(a,k,n);
   }
}
int main() {
   int n, i;
   cout<<"enter no of elements of array\n";
   cin>>n;
   int a[30];
   for (i = 1; i <= n; i++) {
      cout<<"enter elements"<<" "<<(i)<<endl;
      cin>>a[i];
   }
   build_maxheap(a,n);
   cout<<"Max Heap\n";
   for (i = 1; i <= n; i++) {
      cout<<a[i]<<endl;
   }
}