     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
     "pygments_lexer": "ipython3",
     "version": "3.4.3"
    }
   },
   "nbformat": 4,
   "nbformat_minor": 0
  }
 
</s> remove    "version": "3.4.3"
 </s> add    "version": "3.5.0" </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     "* Deletion requires two pointers, one to the previous node and one to the current node\n",
 </s> add 
   "version": "3.5.0"
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
     "pygments_lexer": "ipython3",
   "version": "3.5.0"
    }
   },
   "nbformat": 4,
   "nbformat_minor": 0
  }
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_challenge.ipynb