    }
   ],
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     "display_name": "Python 2",
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</s>
   "display_name": "Python 3",
    }
   ],
   "metadata": {
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   "display_name": "Python 3",
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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