{ "cells": [ { "cell_type": "markdown", "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 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", "
\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",
    "
\n", "\n" ] }, { "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": { "collapsed": false }, "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": { "collapsed": false }, "outputs": [], "source": [ "# %load test_trie.py\n", "from nose.tools import assert_true\n", "\n", "\n", "class TestTrie(object):\n", "\n", " def test_trie(self):\n", " print('Test: Remove from empty trie')\n", " trie = Trie()\n", " assert_true(trie.remove('foo') is None)\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", " assert_true(trie.find(word) is not None)\n", "\n", " # Remove me\n", " # Remove mens\n", " # Remove a\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", " assert_true(trie.find(word) is not None)\n", " for word in words_removed:\n", " assert_true(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", " assert_true(trie.find(word) is not None)\n", " for word in words_removed:\n", " assert_true(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", " assert_true(trie.find(word) is not None)\n", " for word in words_removed:\n", " assert_true(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", " assert_true(trie.find(word) is not None)\n", " for word in words_removed:\n", " assert_true(trie.find(word) is None)\n", "\n", " print('Success: test_trie')\n", "\n", "\n", "def main():\n", " test = TestTrie()\n", " test.test_trie()\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." ] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.5.0" } }, "nbformat": 4, "nbformat_minor": 0 }