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Q:

# max heap c++ stl;

``priority_queue <int> maxHeap; ``
3
``````// 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;
}
``````
1
``````// C++ code to demonstrate the working of
// push_heap() and pop_heap()
#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;

// using push_back() to enter element
// in vector
v1.push_back(50);

// using push_heap() to reorder elements
push_heap(v1.begin(), v1.end());

// Displaying the maximum element of heap
// using front()
cout << "The maximum element of heap after push is : ";
cout << v1.front() << endl;

// using pop_heap() to delete maximum element
pop_heap(v1.begin(), v1.end());
v1.pop_back();

// Displaying the maximum element of heap
// using front()
cout << "The maximum element of heap after pop is : ";
cout << v1.front() << endl;

return 0;
}
``````
1
``````#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;
}
}``````
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