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   "source": [
    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). 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: Swap the odd and even bits of a positive integer with as few operations as possible.\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 input is always a positive int?\n",
    "    * Yes\n",
    "* Can we assume we're working with 32 bits?\n",
    "    * Yes\n",
    "* Is the output an int?\n",
    "    * Yes\n",
    "* Can we assume the inputs are valid (not None)?\n",
    "    * No\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* None -> Exception\n",
    "* 0 -> 0\n",
    "* -1 -> -1\n",
    "* General case\n",
    "<pre>\n",
    "    input  = 1001 1111 0110\n",
    "    result = 0110 1111 1001\n",
    "<pre>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook]().  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": false
   },
   "outputs": [],
   "source": [
    "class Bits(object):\n",
    "\n",
    "    def pairwise_swap(self, num):\n",
    "        # TODO: Implement me\n",
    "        pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**The following unit test is expected to fail until you solve the challenge.**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# %load test_pairwise_swap.py\n",
    "from nose.tools import assert_equal\n",
    "\n",
    "\n",
    "class TestBits(object):\n",
    "\n",
    "    def test_pairwise_swap(self):\n",
    "        bits = Bits()\n",
    "        assert_equal(bits.pairwise_swap(0), 0)\n",
    "        assert_equal(bits.pairwise_swap(1), 1)\n",
    "        num = int('0000100111110110', base=2)\n",
    "        expected = int('0000011011111001', base=2)\n",
    "        assert_equal(bits.pairwise_swap(num), expected)\n",
    "        print('Success: test_pairwise_swap')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestBits()\n",
    "    test.test_pairwise_swap()\n",
    "\n",
    "\n",
    "if __name__ == '__main__':\n",
    "    main()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Solution Notebook\n",
    "\n",
    "Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
   ]
  }
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