Heap sort Algorithm in Python

Author: avinashn

Algorithms/Sorting Algorithms/heap_sort.py

@@ -0,0 +1,54 @@
+__author__ = 'Avinash'
+
+
+def heapify(arr, n, i):
+    """
+    Heapify function to build a max heap from an unsorted array.
+    """
+    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[l] > arr[largest]:
+        largest = l
+
+    # See if right child of root exists and is greater than root
+    if r < n and arr[r] > arr[largest]:
+        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 heap_sort(arr):
+    """
+    Heap sort function to sort an unsorted array in ascending order.
+    """
+    n = len(arr)
+
+    # Build a max heap.
+    for i in range(n // 2 - 1, -1, -1):
+        heapify(arr, n, i)
+
+    # Extract elements one by one
+    for i in range(n-1, 0, -1):
+        arr[i], arr[0] = arr[0], arr[i]  # swap
+        heapify(arr, i, 0)
+
+    print('\nThe sorted list: \t', arr)
+    print('\n')
+
+
+lst = []
+size = int(input("\nEnter size of the list: \t"))
+
+for input_elements in range(size):
+    elements = int(input("Enter the element: \t"))
+    lst.append(elements)
+
+heap_sort(lst)