/
heapsort.py
52 lines (41 loc) · 1.16 KB
/
heapsort.py
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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)
def heapSort(arr):
n = len(arr)
# empty list returns sorted empty list
if n == 0:
return []
# list of size one, returns same list
if n == 1:
return 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)
return arr
# not execute the code when imported
if __name__ == "__main__":
print('Enter a list of numbers')
arr = list(map(int,input().split()))
heapSort(arr)
print('After performing heap sort')
for i in arr:
print(i,end =' ')