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   "metadata": {},
   "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: Implement the method draw_line(screen, width, x1, x2) where screen is a list of bytes, width is divisible by 8, and x1, x2 are absolute pixel positions.\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 inputs are valid?\n",
    "    * No\n",
    "* For the output, do we set corresponding bits in screen?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* Invalid inputs -> Exception\n",
    "    * screen is empty\n",
    "    * width = 0\n",
    "    * any input param is None\n",
    "    * x1 or x2 is out of bounds\n",
    "* General case for len(screen) = 20, width = 32:\n",
    "    * x1 = 2, x2 = 6\n",
    "        * screen[0] = int('00111110', base=2)\n",
    "    * x1 = 68, x2 = 80\n",
    "        * screen[8], int('00001111', base=2)\n",
    "        * screen[9], int('11111111', base=2)\n",
    "        * screen[10], int('10000000', base=2)"
   ]
  },
  {
   "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 BitsScreen(object):\n",
    "\n",
    "    def draw_line(self, screen, width, x1, x2):\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_draw_line.py\n",
    "from nose.tools import assert_equal\n",
    "\n",
    "\n",
    "class TestBitsScreen(object):\n",
    "\n",
    "    def test_draw_line(self):\n",
    "        bits_screen = BitsScreen()\n",
    "        screen = []\n",
    "        for _ in range(20):\n",
    "            screen.append(int('00000000', base=2))\n",
    "        bits_screen.draw_line(screen, width=32, x1=68, x2=80)\n",
    "        assert_equal(screen[8], int('00001111', base=2))\n",
    "        assert_equal(screen[9], int('11111111', base=2))\n",
    "        assert_equal(screen[10], int('10000000', base=2))\n",
    "        bits_screen.draw_line(screen, width=32, x1=2, x2=6)\n",
    "        assert_equal(screen[0], int('00111110', base=2))\n",
    "        bits_screen.draw_line(screen, width=32, x1=10, x2=13)\n",
    "        assert_equal(screen[1], int('00111100', base=2))\n",
    "        print('Success: test_draw_line')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestBitsScreen()\n",
    "    test.test_draw_line()\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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