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   "metadata": {},
   "source": [
    "This notebook was prepared by [Rishi Rajasekaran](https://github.com/rishihot55). Source and license info is available on [Github](https://github.com/donnemartin/interactive-coding-challenges)."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Challenge Notebook"
   ]
  },
  {
   "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",
    "* [Unit Test](#Unit-Test)\n",
    "* [Solution Notebook](#Solution-Notebook)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Constraints\n",
    "\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"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "<pre>\n",
    "* None -> Exception\n",
    "* Negative -> Exception\n",
    "* 0 -> []\n",
    "* 1 -> ['()']\n",
    "* 2 -> ['(())', '()()']\n",
    "* 3 -> ['((()))', '(()())', '(())()', '()(())', '()()()']\n",
    "</pre>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/recursion_dynamic/n_pairs_parentheses/n_pairs_parentheses_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class Parentheses(object):\n",
    "\n",
    "    def find_pair(self, num_pairs):\n",
    "        # TODO: implement me\n",
    "        pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# %load test_n_pairs_parentheses.py\n",
    "from nose.tools import assert_equal, assert_raises\n",
    "\n",
    "\n",
    "class TestPairParentheses(object):\n",
    "\n",
    "    def test_pair_parentheses(self):\n",
    "        parentheses = Parentheses()\n",
    "        assert_raises(TypeError, parentheses.find_pair, None)\n",
    "        assert_raises(ValueError, parentheses.find_pair, -1)\n",
    "        assert_equal(parentheses.find_pair(0), [])\n",
    "        assert_equal(parentheses.find_pair(1), ['()'])\n",
    "        assert_equal(parentheses.find_pair(2), ['(())',\n",
    "                                                '()()'])\n",
    "        assert_equal(parentheses.find_pair(3), ['((()))',\n",
    "                                                '(()())',\n",
    "                                                '(())()',\n",
    "                                                '()(())',\n",
    "                                                '()()()'])\n",
    "        print('Success: test_pair_parentheses')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestPairParentheses()\n",
    "    test.test_pair_parentheses()\n",
    "\n",
    "\n",
    "if __name__ == '__main__':\n",
    "    main()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Solution Notebook\n",
    "\n",
    "Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/recursion_dynamic/n_pairs_parentheses/n_pairs_parentheses_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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