    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Problem: Print all valid combinations of n-pairs of parentheses.\n",
      "\n",
      "* [Constraints](#Constraints)\n",
      "* [Test Cases](#Test-Cases)\n",
      "* [Algorithm](#Algorithm)\n",
      "* [Code](#Code)\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" </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" </s> remove     "* 1 -> [()]\n",
    "* 2 -> [(()), ()()]\n",
    "* 3 -> [((())), (()()), (())(), ()(()), ()()()]"
 </s> add     "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>" </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>"
    "## Problem: Find all valid combinations of n-pairs of parentheses.\n",
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
    "## Problem: Find all valid combinations of n-pairs of parentheses.\n",
      "\n",
      "* [Constraints](#Constraints)\n",
      "* [Test Cases](#Test-Cases)\n",
      "* [Algorithm](#Algorithm)\n",
      "* [Code](#Code)\n",
keep keep keep keep replace keep keep keep keep keep
 Rework n pairs parens challenge (#145) 
recursion_dynamic/n_pairs_parentheses/n_pairs_parentheses_challenge.ipynb