      "* Time: O(n^2)\n",
      "* Space: O(1)\n",
      "\n",
      "Note:\n",
      "* Deletion requires two pointers, one to the previous node and one to the current node\n",
      "* We'll need to use a 'runner' to check every other node and compare it to the current node"
     ]
    },
    {
     "cell_type": "markdown",
 
</s> remove     "* Space: O(n)\n",
    "\n",
    "Note:\n",
    "* Deletion requires two pointers, one to the previous node and one to the current node"
 </s> add     "* Space: O(n)" </s> remove     "        * If the node's value is in the hash map\n",
    "            * Delete the node\n",
    "        * Else\n",
    "            * Add node's value to the hash map\n",
 </s> add     "        * Delete nodes that match current node\n", </s> remove     "* Can you use additional data structures?\n",
    "    * Implement both solutions\n",
 </s> add 
      "* Time: O(n^2)\n",
      "* Space: O(1)\n",
      "\n",
      "Note:\n",

      "* We'll need to use a 'runner' to check every other node and compare it to the current node"
     ]
    },
    {
     "cell_type": "markdown",
keep keep keep keep replace keep keep keep keep keep
 Polish remove duplicates challenge and solution

Update constraints and algorithm discussion. 
linked_lists/remove_duplicates/remove_duplicates_solution.ipynb