From 6b269d0f45268ed55a5d4242c035822b9fe21522 Mon Sep 17 00:00:00 2001
From: Donne Martin <donne.martin@gmail.com>
Date: Sun, 16 Aug 2015 08:21:11 -0400
Subject: [PATCH] Updated bst to keep track of its parent and to return the
 node it inserts.

---
 graphs_trees/bst/bst.py              |  9 +++++++--
 graphs_trees/bst/bst_challenge.ipynb |  4 +++-
 graphs_trees/bst/bst_solution.ipynb  | 13 ++++++++++---
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/graphs_trees/bst/bst.py b/graphs_trees/bst/bst.py
index 38d6814..ce6a16b 100644
--- a/graphs_trees/bst/bst.py
+++ b/graphs_trees/bst/bst.py
@@ -4,6 +4,7 @@ class Node(object):
         self.data = data
         self.left = None
         self.right = None
+        self.parent = None
 
     def __str__(self):
         return str(self.data)
@@ -13,10 +14,14 @@ def insert(root, data):
     if data <= root.data:
         if root.left is None:
             root.left = Node(data)
+            root.left.parent = root
+            return root.left
         else:
-            insert(root.left, data)
+            return insert(root.left, data)
     else:
         if root.right is None:
             root.right = Node(data)
+            root.right.parent = root
+            return root.right
         else:
-            insert(root.right, data)
\ No newline at end of file
+            return insert(root.right, data)
\ No newline at end of file
diff --git a/graphs_trees/bst/bst_challenge.ipynb b/graphs_trees/bst/bst_challenge.ipynb
index 5110969..df23770 100644
--- a/graphs_trees/bst/bst_challenge.ipynb
+++ b/graphs_trees/bst/bst_challenge.ipynb
@@ -38,7 +38,9 @@
     "* Can we assume all left descendents <= n < all right descendents?\n",
     "    * Yes\n",
     "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
-    "    * Yes"
+    "    * Yes\n",
+    "* Do we have to keep track of the parent nodes?\n",
+    "    * This is optional"
    ]
   },
   {
diff --git a/graphs_trees/bst/bst_solution.ipynb b/graphs_trees/bst/bst_solution.ipynb
index 183b1be..36facb0 100644
--- a/graphs_trees/bst/bst_solution.ipynb
+++ b/graphs_trees/bst/bst_solution.ipynb
@@ -38,7 +38,9 @@
     "* Can we assume all left descendents <= n < all right descendents?\n",
     "    * Yes\n",
     "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
-    "    * Yes"
+    "    * Yes\n",
+    "* Do we have to keep track of the parent nodes?\n",
+    "    * This is optional"
    ]
   },
   {
@@ -108,6 +110,7 @@
     "        self.data = data\n",
     "        self.left = None\n",
     "        self.right = None\n",
+    "        self.parent = None\n",
     "\n",
     "    def __str__(self):\n",
     "        return str(self.data)\n",
@@ -117,13 +120,17 @@
     "    if data <= root.data:\n",
     "        if root.left is None:\n",
     "            root.left = Node(data)\n",
+    "            root.left.parent = root\n",
+    "            return root.left\n",
     "        else:\n",
-    "            insert(root.left, data)\n",
+    "            return insert(root.left, data)\n",
     "    else:\n",
     "        if root.right is None:\n",
     "            root.right = Node(data)\n",
+    "            root.right.parent = root\n",
+    "            return root.right\n",
     "        else:\n",
-    "            insert(root.right, data)"
+    "            return insert(root.right, data)"
    ]
   },
   {