      "\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."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
 
</s> remove     "If the `root` input is `None`, return a tree with the only element being the new root node."
 </s> add     "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." </s> remove     "### In-Order Traversal (Provided)\n",
 </s> add     "### In-Order Traversal\n", </s> remove     "### In-Order Traversal (Provided)\n",
 </s> add     "### In-Order Traversal\n", </s> remove     "    * This is optional"
 </s> add     "    * This is optional\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes" </s> remove     "    * This is optional"
 </s> add     "    * This is optional\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes"
    "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."
      "\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.\n",
    "\n",
    "You do not have to code the in-order traversal, it is part of the unit test."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
keep keep keep keep replace keep keep keep keep keep
 Polish bst challenge and solution (#75)

Update constraints, algorithm discussion, and code. 
graphs_trees/bst/bst_challenge.ipynb