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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: Implement n stacks using a single array.\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",
    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
    "\n",
    "* Are the stacks and array a fixed size?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* Test the following on the three stacks:\n",
    "    * Push to full stack -> Exception\n",
    "    * Push to non-full stack\n",
    "    * Pop on empty stack -> Exception\n",
    "    * Pop on non-empty stack"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/stacks_queues/n_stacks/n_stacks_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
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   "outputs": [],
   "source": [
    "class Stacks(object):\n",
    "    \n",
    "    def __init__(self, num_stacks, stack_size):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def abs_index(self, stack_index):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def push(self, stack_index, data):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def pop(self, stack_index):\n",
    "        # TODO: Implement me\n",
    "        pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test\n",
    "\n",
    "\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_n_stacks.py\n",
    "from nose.tools import assert_equal\n",
    "from nose.tools import raises\n",
    "\n",
    "\n",
    "class TestStacks(object):\n",
    "    \n",
    "    @raises(Exception)\n",
    "    def test_pop_on_empty(self, num_stacks, stack_size):\n",
    "        print('Test: Pop on empty stack')\n",
    "        stacks = Stacks(num_stacks, stack_size)\n",
    "        stacks.pop(0)\n",
    "\n",
    "    @raises(Exception)\n",
    "    def test_push_on_full(self, num_stacks, stack_size):\n",
    "        print('Test: Push to full stack')\n",
    "        stacks = Stacks(num_stacks, stack_size)\n",
    "        for i in xrange(0, stack_size):\n",
    "            stacks.push(2, i)\n",
    "        stacks.push(2, stack_size)\n",
    "\n",
    "    def test_stacks(self, num_stacks, stack_size):\n",
    "        print('Test: Push to non-full stack')\n",
    "        stacks = Stacks(num_stacks, stack_size)\n",
    "        stacks.push(0, 1)\n",
    "        stacks.push(0, 2)\n",
    "        stacks.push(1, 3)\n",
    "        stacks.push(2, 4)\n",
    "\n",
    "        print('Test: Pop on non-empty stack')\n",
    "        assert_equal(stacks.pop(0), 2)\n",
    "        assert_equal(stacks.pop(0), 1)\n",
    "        assert_equal(stacks.pop(1), 3)\n",
    "        assert_equal(stacks.pop(2), 4)\n",
    "\n",
    "        print('Success: test_stacks\\n')\n",
    "\n",
    "def main():\n",
    "    num_stacks = 3\n",
    "    stack_size = 100    \n",
    "    test = TestStacks()\n",
    "    test.test_pop_on_empty(num_stacks, stack_size)\n",
    "    test.test_push_on_full(num_stacks, stack_size)\n",
    "    test.test_stacks(num_stacks, stack_size)\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/stacks_queues/n_stacks/n_stacks_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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