      "    * Singly\n",
      "* Is this a circular list?\n",
      "    * No\n",
      "* Do we keep track of the tail or just the head?\n",
      "    * Just the head"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
 
</s> remove     "    * Just the head"
 </s> add     "    * Just the head\n",
    "* Can we insert None values?\n",
    "    * No" </s> remove     "* Create a node with the input data\n",
    "* If this is an empty list\n",
    "    * Assign the head to the node\n",
    "* Else\n",
    "    * Set the node.next to the head\n",
    "    * Set the head to the node\n",
 </s> add     "* Create a node with the input data, set node.next to head\n",
    "* Assign the head to the node\n", </s> remove    "display_name": "Python 2",
 </s> add    "display_name": "Python 3", </s> remove    "display_name": "Python 2",
 </s> add    "display_name": "Python 3",
    "    * Just the head\n",
    "* Can we insert None values?\n",
    "    * No"
      "    * Singly\n",
      "* Is this a circular list?\n",
      "    * No\n",
      "* Do we keep track of the tail or just the head?\n",
    "    * Just the head\n",
    "* Can we insert None values?\n",
    "    * No"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
keep keep keep keep replace keep keep keep keep keep
 Polish linked list challenge and solution

Update algorithm discussion, solution, and constraints. 
linked_lists/linked_list/linked_list_challenge.ipynb