     "source": [
      "## Test Cases\n",
      "\n",
      "* 0 -> []\n",
      "* 1 -> [()]\n",
      "* 2 -> [(()), ()()]\n",
      "* 3 -> [((())), (()()), (())(), ()(()), ()()()]"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
 
</s> remove     "* 0 -> ' '\n",
    "* 1 -> ()\n",
    "* 2 -> (()), ()()\n",
    "* 3 -> ((())), (()()), (())(), ()(()), ()()()"
 </s> add     "<pre>\n",
    "* None -> Exception\n",
    "* Negative -> Exception\n",
    "* 0 -> []\n",
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>" </s> remove     "## Problem: Print all valid combinations of n-pairs of parentheses.\n",
 </s> add     "## Problem: Find all valid combinations of n-pairs of parentheses.\n", </s> remove     "## Problem: Print all valid combinations of n-pairs of parentheses.\n",
 </s> add     "## Problem: Find all valid combinations of n-pairs of parentheses.\n", </s> remove     "* None"
 </s> add     "\n",
    "* Is the input an integer representing the number of pairs?\n",
    "    * Yes\n",
    "* Can we assume the inputs are valid?\n",
    "    * No\n",
    "* Is the output a list of valid combinations?\n",
    "    * Yes\n",
    "* Should the output have duplicates?\n",
    "    * No\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>"
     "source": [
      "## Test Cases\n",
      "\n",
      "* 0 -> []\n",
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>"
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>"
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
keep keep keep keep replace replace replace keep keep keep keep keep
 Rework n pairs parens challenge (#145) 
recursion_dynamic/n_pairs_parentheses/n_pairs_parentheses_challenge.ipynb