[ADD] heap sort with pure function

Python/heap_sort_pure.py

@@ -0,0 +1,48 @@
+# Heap Sort
+
+
+def heapify(arr, n, i):
+    largest = i
+    left = 2 * i + 1	 # left = 2*i + 1
+    right = 2 * i + 2	 # right = 2*i + 2
+
+    # See if left child of root exists and is
+    # greater than root
+    if left < n and arr[i] < arr[left]:
+        largest = left
+
+    # See if right child of root exists and is
+    # greater than root
+    if right < n and arr[largest] < arr[right]:
+        largest = right
+
+    # Change root, if needed
+    if largest != i:
+        arr[i], arr[largest] = arr[largest], arr[i]
+        heapify(arr, n, largest)
+
+
+def heap_sort(input_list):
+    size = len(input_list)
+    result_array = input_list[:]
+
+    # Build a max heap.
+    for i in range(size, -1, -1):
+        heapify(result_array, size, i)
+
+    # One by one extract elements
+    for i in range(size-1, 0, -1):
+        result_array[i], result_array[0] = result_array[0], result_array[i]
+        heapify(result_array, i, 0)
+
+    return result_array
+
+
+if __name__ == '__main__':
+    sample = [12, 11, 13, 5, 6, 7]
+
+    print("Sorted array:")
+    print(sample)
+
+    print("Sorted array:")
+    print(heap_sort(sample))