From c24a6283294d0673a1e41c43f2f44f6868f1648e Mon Sep 17 00:00:00 2001
From: Donne Martin <donne.martin@gmail.com>
Date: Fri, 24 Jun 2016 07:23:20 -0400
Subject: [PATCH] Polish bst challenge and solution (#75)

Update constraints, algorithm discussion, and code.
---
 graphs_trees/bst/bst.py              | 11 +++++------
 graphs_trees/bst/bst_challenge.ipynb | 14 ++++++++++----
 graphs_trees/bst/bst_solution.ipynb  | 25 +++++++++++++++----------
 3 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/graphs_trees/bst/bst.py b/graphs_trees/bst/bst.py
index 57df388..39a9836 100644
--- a/graphs_trees/bst/bst.py
+++ b/graphs_trees/bst/bst.py
@@ -11,20 +11,19 @@ class Node(object):
 
 
 def insert(root, data):
+    # Constraint: Assume we are working with valid ints
     if root is None:
         root = Node(data)
         return root
     if data <= root.data:
         if root.left is None:
-            root.left = Node(data)
+            root.left = insert(root.left, data)
             root.left.parent = root
-            return root.left
         else:
-            return insert(root.left, data)
+            insert(root.left, data)
     else:
         if root.right is None:
-            root.right = Node(data)
+            root.right = insert(root.right, data)
             root.right.parent = root
-            return root.right
         else:
-            return insert(root.right, data)
\ No newline at end of file
+            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 a3c1a34..bcf6340 100644
--- a/graphs_trees/bst/bst_challenge.ipynb
+++ b/graphs_trees/bst/bst_challenge.ipynb
@@ -33,6 +33,8 @@
    "source": [
     "## Constraints\n",
     "\n",
+    "* Can we insert None values?\n",
+    "    * No\n",
     "* Can we assume we are working with valid integers?\n",
     "    * Yes\n",
     "* Can we assume all left descendents <= n < all right descendents?\n",
@@ -40,7 +42,9 @@
     "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
     "    * Yes\n",
     "* Do we have to keep track of the parent nodes?\n",
-    "    * This is optional"
+    "    * This is optional\n",
+    "* Can we assume this fits in memory?\n",
+    "    * Yes"
    ]
   },
   {
@@ -53,12 +57,14 @@
     "\n",
     "Insert will be tested through the following traversal:\n",
     "\n",
-    "### In-Order Traversal (Provided)\n",
+    "### In-Order Traversal\n",
     "\n",
     "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
     "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
     "\n",
-    "If the `root` input is `None`, return a tree with the only element being the new root node."
+    "If the `root` input is `None`, return a tree with the only element being the new root node.\n",
+    "\n",
+    "You do not have to code the in-order traversal, it is part of the unit test."
    ]
   },
   {
@@ -206,7 +212,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.4.3"
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,
diff --git a/graphs_trees/bst/bst_solution.ipynb b/graphs_trees/bst/bst_solution.ipynb
index 54f9445..3bab5e0 100644
--- a/graphs_trees/bst/bst_solution.ipynb
+++ b/graphs_trees/bst/bst_solution.ipynb
@@ -33,6 +33,8 @@
    "source": [
     "## Constraints\n",
     "\n",
+    "* Can we insert None values?\n",
+    "    * No\n",
     "* Can we assume we are working with valid integers?\n",
     "    * Yes\n",
     "* Can we assume all left descendents <= n < all right descendents?\n",
@@ -40,7 +42,9 @@
     "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
     "    * Yes\n",
     "* Do we have to keep track of the parent nodes?\n",
-    "    * This is optional"
+    "    * This is optional\n",
+    "* Can we assume this fits in memory?\n",
+    "    * Yes"
    ]
   },
   {
@@ -53,12 +57,14 @@
     "\n",
     "Insert will be tested through the following traversal:\n",
     "\n",
-    "### In-Order Traversal (Provided)\n",
+    "### In-Order Traversal\n",
     "\n",
     "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
     "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
     "\n",
-    "If the `root` input is `None`, return a tree with the only element being the new root node."
+    "If the `root` input is `None`, return a tree with the only element being the new root node.\n",
+    "\n",
+    "You do not have to code the in-order traversal, it is part of the unit test."
    ]
   },
   {
@@ -122,23 +128,22 @@
     "\n",
     "\n",
     "def insert(root, data):\n",
+    "    # Constraint: Assume we are working with valid ints\n",
     "    if root is None:\n",
     "        root = Node(data)\n",
     "        return root\n",
     "    if data <= root.data:\n",
     "        if root.left is None:\n",
-    "            root.left = Node(data)\n",
+    "            root.left = insert(root.left, data)\n",
     "            root.left.parent = root\n",
-    "            return root.left\n",
     "        else:\n",
-    "            return insert(root.left, data)\n",
+    "            insert(root.left, data)\n",
     "    else:\n",
     "        if root.right is None:\n",
-    "            root.right = Node(data)\n",
+    "            root.right = insert(root.right, data)\n",
     "            root.right.parent = root\n",
-    "            return root.right\n",
     "        else:\n",
-    "            return insert(root.right, data)"
+    "            insert(root.right, data)"
    ]
   },
   {
@@ -272,7 +277,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.4.3"
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,