      "    * 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>
    "    * 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_solution.ipynb