Create heapsort.py

Algorithms/Sorting_Algorithms/heapsort.py

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+def heapify(nums, heap_size, root_index):
+    # Assume the index of the largest element is the root index
+    largest = root_index
+    left_child = (2 * root_index) + 1
+    right_child = (2 * root_index) + 2
+
+    # If the left child of the root is a valid index, and the element is greater
+    # than the current largest element, then update the largest element
+    if left_child < heap_size and nums[left_child] > nums[largest]:
+        largest = left_child
+
+    # Do the same for the right child of the root
+    if right_child < heap_size and nums[right_child] > nums[largest]:
+        largest = right_child
+
+    # If the largest element is no longer the root element, swap them
+    if largest != root_index:
+        nums[root_index], nums[largest] = nums[largest], nums[root_index]
+        # Heapify the new root element to ensure it's the largest
+        heapify(nums, heap_size, largest)
+
+
+def heap_sort(nums):
+    n = len(nums)
+
+    # Create a Max Heap from the list
+    # The 2nd argument of range means we stop at the element before -1 i.e.
+    # the first element of the list.
+    # The 3rd argument of range means we iterate backwards, reducing the count
+    # of i by 1
+    for i in range(n, -1, -1):
+        heapify(nums, n, i)
+
+    # Move the root of the max heap to the end of
+    for i in range(n - 1, 0, -1):
+        nums[i], nums[0] = nums[0], nums[i]
+        heapify(nums, i, 0)
+
+
+# Verify it works
+random_list_of_nums = [55, 43, 12, 4, 23]
+heap_sort(random_list_of_nums)
+print(random_list_of_nums)