Hailey M. cs-fun-class-a

binary_search_trees/array_to_bst.py

@@ -1,13 +1,29 @@
+from hashlib import new
+
+
 class TreeNode:
     def __init__(self, value, left = None, right = None):
         self.val = value
         self.left = left
         self.right = right
 
 
+def helper(arr, left, right):
+    if left > right:
+        return None
+    mid = (left + right) // 2
+    new_node = TreeNode(arr[mid])
+    new_node.left = helper(arr, left, mid-1)
+    new_node.right = helper(arr, mid+1, right)
+    return 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 arr is empty, return None
+    if not arr:
+        return None
+
+    return helper(arr, 0, len(arr)-1)