      "    * Yes\n",
      "* Does popping from an empty stack result in an exception?\n",
      "    * Yes\n",
      "* Can we assume the user passed in stack index is valid?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
 
</s> remove     "        self.stack_pointers = [-1] * num_stacks\n",
    "        self.stack_array = [None] * num_stacks * stack_size\n",
 </s> add     "        self.stack_pointers = [-1] * self.num_stacks\n",
    "        self.stack_array = [None] * self.num_stacks * self.stack_size\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
      "    * Yes\n",
      "* Does popping from an empty stack result in an exception?\n",
      "    * Yes\n",
      "* Can we assume the user passed in stack index is valid?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
keep keep keep add keep keep keep keep keep
 Update queue from stacks challenge (#111)

Update test cases and __init__ method. 
stacks_queues/n_stacks/n_stacks_challenge.ipynb