Answers for "what is max heap"

max heap c++ stl;

// 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; 
}

min max heap java

// min heap: PriorityQueue implementation from the JDK
PriorityQueue<Integer> prq = new PriorityQueue<>();

// max heap: PriorityQueue implementation WITH CUSTOM COMPARATOR PASSED
// Method 1: Using Collections (recommended)
PriorityQueue<Integer> prq = new PriorityQueue<>(Collections.reverseOrder());
// Method 2: Using Lambda function (may cause Integer Overflow)
PriorityQueue<Integer> prq = new PriorityQueue<>((a, b) -> b - a);

minimum and maximum numbers of elements in a heap of height h

Hence the minimum number of nodes possible in a heap of height h is 2h.
Clearly a heap of height h, has the maximum number of elements when its lowest level is completely filled.
In this case the heap is a complete binary tree of height h and hence has 2h+1 -1 nodes.

Max Heap Python

def max_heapify(A,k):
    l = left(k)
    r = right(k)
    if l < len(A) and A[l] > A[k]:
        largest = l
    else:
        largest = k
    if r < len(A) and A[r] > A[largest]:
        largest = r
    if largest != k:
        A[k], A[largest] = A[largest], A[k]
        max_heapify(A, largest)

def left(k):
    return 2 * k + 1

def right(i):
    return 2 * k + 2

def build_max_heap(A):
    n = int((len(A)//2)-1)
    for k in range(n, -1, -1):
        max_heapify(A,k)

A = [3,9,2,1,4,5]
build_max_heap(A)
print(A)