Create Heapsort.py

Sorting Algorithms/Heapsort.py

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+# heapify
+def heapify(arr, n, i):
+   largest = i # largest value
+   l = 2 * i + 1 # left
+   r = 2 * i + 2 # right
+   # if left child exists
+   if l < n and arr[i] < arr[l]:
+      largest = l
+   # if right child exits
+   if r < n and arr[largest] < arr[r]:
+      largest = r
+   # root
+   if largest != i:
+      arr[i],arr[largest] = arr[largest],arr[i] # swap
+      # root.
+      heapify(arr, n, largest)
+# sort
+def heapSort(arr):
+   n = len(arr)
+   # maxheap
+   for i in range(n, -1, -1):
+      heapify(arr, n, i)
+   # element extraction
+   for i in range(n-1, 0, -1):
+      arr[i], arr[0] = arr[0], arr[i] # swap
+      heapify(arr, i, 0)
+# main
+arr = [2,5,3,8,6,5,4,7]
+heapSort(arr)
+n = len(arr)
+print ("Sorted array is")
+for i in range(n):
+   print (arr[i],end=" ")