interactive-coding-challenges/graphs_trees/trie/trie_challenge.ipynb

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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: Implement a trie with find, insert, remove, and list_words methods.\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 we are working with strings?\n",
    "    * Yes\n",
    "* Are the strings in ASCII?\n",
    "    * Yes\n",
    "* Should `find` only match exact words with a terminating character?\n",
    "    * Yes\n",
    "* Should `list_words` only return words with a terminating character?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "<pre>\n",
    "\n",
    "         root\n",
    "       /  |  \\\n",
    "      h   a*  m\n",
    "     / \\   \\   \\\n",
    "    a   e*  t*  e*\n",
    "   / \\         / \\\n",
    "  s*  t*      n*  t*\n",
    "             /\n",
    "            s*\n",
    "\n",
    "find\n",
    "\n",
    "* Find on an empty trie\n",
    "* Find non-matching\n",
    "* Find matching\n",
    "\n",
    "insert\n",
    "\n",
    "* Insert on empty trie\n",
    "* Insert to make a leaf terminator char\n",
    "* Insert to extend an existing terminator char\n",
    "\n",
    "remove\n",
    "\n",
    "* Remove me\n",
    "* Remove mens\n",
    "* Remove a\n",
    "* Remove has\n",
    "\n",
    "list_words\n",
    "\n",
    "* List empty\n",
    "* List general case\n",
    "</pre>\n",
    "\n"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/trie/trie_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": [
    "from collections import OrderedDict\n",
    "\n",
    "\n",
    "class Node(object):\n",
    "\n",
    "    def __init__(self, data, parent=None, terminates=False):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "\n",
    "class Trie(object):\n",
    "\n",
    "    def __init__(self):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def find(self, word):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def insert(self, word):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def remove(self, word):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def list_words(self):\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": {},
   "outputs": [],
   "source": [
    "# %load test_trie.py\n",
    "import unittest\n",
    "\n",
    "\n",
    "class TestTrie(unittest.TestCase):       \n",
    "\n",
    "    def test_trie(self):\n",
    "        trie = Trie()\n",
    "\n",
    "        print('Test: Insert')\n",
    "        words = ['a', 'at', 'has', 'hat', 'he',\n",
    "                 'me', 'men', 'mens', 'met']\n",
    "        for word in words:\n",
    "            trie.insert(word)\n",
    "        for word in trie.list_words():\n",
    "            self.assertTrue(trie.find(word) is not None)\n",
    "            \n",
    "        print('Test: Remove me')\n",
    "        trie.remove('me')\n",
    "        words_removed = ['me']\n",
    "        words = ['a', 'at', 'has', 'hat', 'he',\n",
    "                 'men', 'mens', 'met']\n",
    "        for word in words:\n",
    "            self.assertTrue(trie.find(word) is not None)\n",
    "        for word in words_removed:\n",
    "            self.assertTrue(trie.find(word) is None)\n",
    "\n",
    "        print('Test: Remove mens')\n",
    "        trie.remove('mens')\n",
    "        words_removed = ['me', 'mens']\n",
    "        words = ['a', 'at', 'has', 'hat', 'he',\n",
    "                 'men', 'met']\n",
    "        for word in words:\n",
    "            self.assertTrue(trie.find(word) is not None)\n",
    "        for word in words_removed:\n",
    "            self.assertTrue(trie.find(word) is None)\n",
    "\n",
    "        print('Test: Remove a')\n",
    "        trie.remove('a')\n",
    "        words_removed = ['a', 'me', 'mens']\n",
    "        words = ['at', 'has', 'hat', 'he',\n",
    "                 'men', 'met']\n",
    "        for word in words:\n",
    "            self.assertTrue(trie.find(word) is not None)\n",
    "        for word in words_removed:\n",
    "            self.assertTrue(trie.find(word) is None)\n",
    "\n",
    "        print('Test: Remove has')\n",
    "        trie.remove('has')\n",
    "        words_removed = ['a', 'has', 'me', 'mens']\n",
    "        words = ['at', 'hat', 'he',\n",
    "                 'men', 'met']\n",
    "        for word in words:\n",
    "            self.assertTrue(trie.find(word) is not None)\n",
    "        for word in words_removed:\n",
    "            self.assertTrue(trie.find(word) is None)\n",
    "\n",
    "        print('Success: test_trie')\n",
    "\n",
    "    def test_trie_remove_invalid(self):\n",
    "        print('Test: Remove from empty trie')\n",
    "        trie = Trie()\n",
    "        self.assertTrue(trie.remove('foo') is None) \n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestTrie()\n",
    "    test.test_trie()\n",
    "    test.assertRaises(KeyError, test.test_trie_remove_invalid)\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/graphs_trees/trie/trie_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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