Emily Saeli - C-17 Whales

binary_search_trees/array_to_bst.py

@@ -5,9 +5,51 @@ def __init__(self, value, left = None, right = None):
         self.right = right
 
 
+
+# class Tree:
+#     def __init__(self):
+#         self.root = None
+
+#     def add_helper(self, current_node, new_node):
+#         if new_node.val < current_node.val:
+#             if not current_node.left:
+#                 current_node.left = new_node
+#                 return
+#             else:
+#                 self.add_helper(current_node.left, new_node)
+#         elif new_node.val >= current_node.val:
+#             if not current_node.right:
+#                 current_node.right = new_node
+#                 return
+#             else:
+#                 self.add_helper(current_node.right, new_node)
+
+#     def add(self, val):
+#         new_node = TreeNode(val)
+#         if not self.root:
+#             self.root = new_node
+#         else:
+#             self.add_helper(self.root, new_node)
+
 def arr_to_bst(arr):
     """ Given a sorted array, write a function to create a 
         Balanced Binary Search Tree using the elements in the array.
         Return the root of the Binary Search Tree.
     """
-    pass
+    if not arr:
+        return None
+    elif len(arr) == 1:
+        return TreeNode(arr[0])
+    else:
+        if len(arr)% 2 == 0:
+            median_index = int(len(arr)/2)
+            median = arr[median_index]
+        else:
+            median_index = int((len(arr)-1)/2)
+            median = arr[median_index]
+        arr_left = arr[0:median_index]
+        arr_right = arr[median_index+1:]
+        median_node = TreeNode(median)
+        median_node.left = arr_to_bst(arr_left)
+        median_node.right = arr_to_bst(arr_right)
+        return median_node

requirements.txt

@@ -4,5 +4,5 @@ packaging==20.8
 pluggy==0.13.1
 py==1.10.0
 pyparsing==2.4.7
-pytest==6.2.1
+pytest==7.2.0
 toml==0.10.2