Question

Hi, so for my homework assignment, we are meant to change this function so that instead of making a list from the array going up in an ascending order, making it be listed in descending order, meaning going from largest number to smallest number, the code I have now works for the ascending order, but how would I change this for it to go descending? Any help would be amazing, and please with a tutorial, thanks so much.

def heapify(arr, n, i):
	largest = i # Initialize largest as root
	l = 2 * i + 1 # left = 2*i + 1
	r = 2 * i + 2 # right = 2*i + 2
	# See if left child of root exists and is
	# greater than root
	if l < n and arr[i] < 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)

Answer 1

def heapify(arr, n, i):
    smallest = i  # Initialize smallest as root 
    l = 2 * i + 1  # left = 2*i + 1 
    r = 2 * i + 2  # right = 2*i + 2 

    # See if left child of root exists and is 
    # less than root 
    if l < n and arr[i] >= arr[l]:
        smallest = l

    # See if right child of root exists and is 
    # less than root 
    if r < n and arr[smallest] >= arr[r]:
        smallest = r

    if smallest != i:
        arr[i], arr[smallest] = arr[smallest], arr[i]  # swap 

        # Heapify the root. 
        heapify(arr, n, smallest)

    # The main function to sort an array of given size 


def heapSort(arr):
    n = len(arr)

    # Build a maxheap. 
    for i in range(n, -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)

    # Driver code to test above 


arr = [12, 11, 13, 5, 6, 7]
heapSort(arr)
n = len(arr)
print("Sorted array is")
for i in range(n):
    print("%d" % arr[i]),

Sorted array is 13 12 12 11 7 6