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   "metadata": {},
   "source": [
    "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Challenge Notebook"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Problem: Implement a function to reverse a string (a list of characters), in-place.\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",
    "* Can we assume the string is ASCII?\n",
    "    * Yes\n",
    "    * Note: Unicode strings could require special handling depending on your language\n",
    "* Since we need to do this in-place, it seems we cannot use the slice operator or the reversed function?\n",
    "    * Correct\n",
    "* Since Python string are immutable, can we use a list of characters instead?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* None -> None\n",
    "* [''] -> ['']\n",
    "* ['f', 'o', 'o', ' ', 'b', 'a', 'r'] -> ['r', 'a', 'b', ' ', 'o', 'o', 'f']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_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": {},
   "outputs": [],
   "source": [
    "class ReverseString(object):\n",
    "\n",
    "    def reverse(self, chars):\n",
    "        # TODO: Implement me\n",
    "        pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\n",
    "\n",
    "**The following unit test is expected to fail until you solve the challenge.**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# %load test_reverse_string.py\n",
    "import unittest\n",
    "\n",
    "\n",
    "class TestReverse(unittest.TestCase):\n",
    "\n",
    "    def test_reverse(self, func):\n",
    "        self.assertEqual(func(None), None)\n",
    "        self.assertEqual(func(['']), [''])\n",
    "        self.assertEqual(func(\n",
    "            ['f', 'o', 'o', ' ', 'b', 'a', 'r']),\n",
    "            ['r', 'a', 'b', ' ', 'o', 'o', 'f'])\n",
    "        print('Success: test_reverse')\n",
    "\n",
    "    def test_reverse_inplace(self, func):\n",
    "        target_list = ['f', 'o', 'o', ' ', 'b', 'a', 'r']\n",
    "        func(target_list)\n",
    "        self.assertEqual(target_list, ['r', 'a', 'b', ' ', 'o', 'o', 'f'])\n",
    "        print('Success: test_reverse_inplace')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestReverse()\n",
    "    reverse_string = ReverseString()\n",
    "    test.test_reverse(reverse_string.reverse)\n",
    "    test.test_reverse_inplace(reverse_string.reverse)\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/arrays_strings/reverse_string/reverse_string_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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