c-17 jaeclayton

binary_search_trees/array_to_bst.py

@@ -5,9 +5,54 @@ def __init__(self, value, left = None, right = None):
         self.right = right
 
 
+
 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.
+
+
+        `arr = [5, 10, 15, 20, 25, 30, 35, 40, 45]`
+
+                        25 
+                     /      \
+                    15        35
+                   / \        / \
+                 10   20     30  40
+                /                  \
+               5                    45
     """
-    pass
+    if not arr: 
+        return None 
+    mid = len(arr)//2 
+    # find midpoint each time the function is recursively called 
+    current_node = TreeNode(arr[mid])
+    # grab left side of mid 
+    #  recursively call function to find mid of left side 
+    current_node.left = arr_to_bst(arr[:mid])
+    # grab right side of mid, skip mid, recursively call to find mid of right side 
+    current_node.right = arr_to_bst(arr[mid + 1:])
+
+    return current_node 
+
+
+
+# # create helper function to print result 
+# def preOrderNodes(current_node): 
+#     if not current_node: 
+#         return 
+#     print(current_node.val)
+#     preOrderNodes(current_node.left)
+#     preOrderNodes(current_node.right)
+
+
+# arr = arr_to_bst([5, 10, 15, 20, 25, 30, 35, 40, 45])
+# preOrderNodes(arr)
+
+
+
+
+
+
+
+