# Python program for implementation of heap Sort
 
# To heapify subtree rooted at index i.
# n is size of heap
 
def leftChild(i):
    return 2 * i + 1

def rightChild(i):
    return 2 * i + 2

def heapify(arr, n, i):
    largest = i  # Initialize largest as root
    l = leftChild(i)
    r = rightChild(i)
 
    # See if left child of root exists and is
    # greater than root
    if l < n and arr[largest] < arr[l]:
        largest = l
 
    # See if right child of root exists and is
    # greater than root
    if r < n and arr[largest] < arr[r]:
        largest = r
 
    # Change root, if needed
    if largest != i:
        arr[i], arr[largest] = arr[largest], arr[i]  # swap
 
        # Heapify the root.
        heapify(arr, n, largest)
 
# The main function to sort an array of given size
 
def heapSort(arr):
    n = len(arr)
 
    # Build a maxheap.
    for i in range(n//2 - 1, -1, -1):
        heapify(arr, n, i)
 
    # One by one extract elements
    for i in range(n-1, 0, -1):
        arr[i], arr[0] = arr[0], arr[i]  # swap
        heapify(arr, i, 0)