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   "source": [
    "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).</i></small>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Challenge Notebook"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Problem: Partition a linked list around a value x, such that all nodes less than x come before all nodes greater than or equal to x.\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 create additional data structures?\n",
    "    * Yes\n",
    "* Do you expect the function to return a new list?\n",
    "    * Yes\n",
    "* Can we assume the input x is valid?\n",
    "    * Yes\n",
    "* Can we assume we already have a linked list class that can be used for this problem?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* Empty list -> []\n",
    "* One element list -> [element]\n",
    "* Left linked list is empty\n",
    "* Right linked list is empty\n",
    "* General case\n",
    "    * Partition = 10\n",
    "    * Input:  4, 3, 7, 8, 10, 1, 10, 12\n",
    "    * Output: 4, 3, 7, 8, 1, 10, 10, 12"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/linked_lists/partition/partition_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,
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    "collapsed": true
   },
   "outputs": [],
   "source": [
    "%run ../linked_list/linked_list.py\n",
    "%load ../linked_list/linked_list.py"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "class MyLinkedList(LinkedList):\n",
    "\n",
    "    def partition(self, data):\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,
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   "source": [
    "# %load test_partition.py\n",
    "from nose.tools import assert_equal\n",
    "\n",
    "\n",
    "class TestPartition(object):\n",
    "\n",
    "    def test_partition(self):\n",
    "        print('Test: Empty list')\n",
    "        linked_list = MyLinkedList(None)\n",
    "        linked_list.partition(10)\n",
    "        assert_equal(linked_list.get_all_data(), [])\n",
    "\n",
    "        print('Test: One element list, left list empty')\n",
    "        linked_list = MyLinkedList(Node(5))\n",
    "        linked_list.partition(0)\n",
    "        assert_equal(linked_list.get_all_data(), [5])\n",
    "\n",
    "        print('Test: Right list is empty')\n",
    "        linked_list = MyLinkedList(Node(5))\n",
    "        linked_list.partition(10)\n",
    "        assert_equal(linked_list.get_all_data(), [5])\n",
    "\n",
    "        print('Test: General case')\n",
    "        # Partition = 10\n",
    "        # Input: 4, 3, 7, 8, 10, 1, 10, 12\n",
    "        # Output: 4, 3, 7, 8, 1, 10, 10, 12\n",
    "        linked_list = MyLinkedList(Node(12))\n",
    "        linked_list.insert_to_front(10)\n",
    "        linked_list.insert_to_front(1)\n",
    "        linked_list.insert_to_front(10)\n",
    "        linked_list.insert_to_front(8)\n",
    "        linked_list.insert_to_front(7)\n",
    "        linked_list.insert_to_front(3)\n",
    "        linked_list.insert_to_front(4)\n",
    "        partitioned_list = linked_list.partition(10)\n",
    "        assert_equal(partitioned_list.get_all_data(),\n",
    "                     [4, 3, 7, 8, 1, 10, 10, 12])\n",
    "\n",
    "        print('Success: test_partition')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestPartition()\n",
    "    test.test_partition()\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/linked_lists/partition/partition_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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