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https://github.com/donnemartin/interactive-coding-challenges
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Add trie challenge
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Donne Martin
279
graphs_trees/trie/trie_challenge.ipynb
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279
graphs_trees/trie/trie_challenge.ipynb
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"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)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Challenge Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Implement a trie with find, insert, remove, and list_words methods.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)\n",
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"* [Solution Notebook](#Solution-Notebook)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Can we assume we are working with strings?\n",
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" * Yes\n",
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"* Are the strings in ASCII?\n",
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" * Yes\n",
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"* Should `find` only match exact words with a terminating character?\n",
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" * Yes\n",
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"* Should `list_words` only return words with a terminating character?\n",
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" * Yes\n",
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"* Can we assume this fits memory?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"<pre>\n",
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"\n",
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" root\n",
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" / | \\\n",
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" h a* m\n",
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" / \\ \\ \\\n",
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" a e* t* e*\n",
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" / \\ / \\\n",
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" s* t* n* t*\n",
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" /\n",
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" s*\n",
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"\n",
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"find\n",
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"\n",
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"* Find on an empty trie\n",
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"* Find non-matching\n",
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"* Find matching\n",
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"\n",
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"insert\n",
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"\n",
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"* Insert on empty trie\n",
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"* Insert to make a leaf terminator char\n",
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"* Insert to extend an existing terminator char\n",
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"\n",
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"remove\n",
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"\n",
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"* Remove me\n",
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"* Remove mens\n",
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"* Remove a\n",
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"* Remove has\n",
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"\n",
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"list_words\n",
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"\n",
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"* List empty\n",
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"* List general case\n",
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"</pre>\n",
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"\n"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"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."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"from collections import OrderedDict\n",
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"\n",
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"\n",
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"class Node(object):\n",
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"\n",
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" def __init__(self, data, parent=None, terminates=False):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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"\n",
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"class Trie(object):\n",
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"\n",
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" def __init__(self):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def find(self, word):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def insert(self, word):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def remove(self, word):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def list_words(self):\n",
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" # TODO: Implement me\n",
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" pass"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"**The following unit test is expected to fail until you solve the challenge.**"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# %load test_trie.py\n",
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"from nose.tools import assert_true\n",
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"\n",
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"\n",
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"class TestTrie(object):\n",
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"\n",
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" def test_trie(self):\n",
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" print('Test: Remove from empty trie')\n",
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" trie = Trie()\n",
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" assert_true(trie.remove('foo') is None)\n",
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"\n",
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" print('Test: Insert')\n",
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" words = ['a', 'at', 'has', 'hat', 'he',\n",
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" 'me', 'men', 'mens', 'met']\n",
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" for word in words:\n",
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" trie.insert(word)\n",
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" for word in trie.list_words():\n",
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" assert_true(trie.find(word) is not None)\n",
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"\n",
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" # Remove me\n",
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" # Remove mens\n",
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" # Remove a\n",
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" \n",
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" print('Test: Remove me')\n",
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" trie.remove('me')\n",
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" words_removed = ['me']\n",
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" words = ['a', 'at', 'has', 'hat', 'he',\n",
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" 'men', 'mens', 'met']\n",
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" for word in words:\n",
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" assert_true(trie.find(word) is not None)\n",
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" for word in words_removed:\n",
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" assert_true(trie.find(word) is None)\n",
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"\n",
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" print('Test: Remove mens')\n",
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" trie.remove('mens')\n",
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" words_removed = ['me', 'mens']\n",
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" words = ['a', 'at', 'has', 'hat', 'he',\n",
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" 'men', 'met']\n",
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" for word in words:\n",
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" assert_true(trie.find(word) is not None)\n",
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" for word in words_removed:\n",
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" assert_true(trie.find(word) is None)\n",
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"\n",
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" print('Test: Remove a')\n",
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" trie.remove('a')\n",
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" words_removed = ['a', 'me', 'mens']\n",
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" words = ['at', 'has', 'hat', 'he',\n",
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" 'men', 'met']\n",
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" for word in words:\n",
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" assert_true(trie.find(word) is not None)\n",
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" for word in words_removed:\n",
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" assert_true(trie.find(word) is None)\n",
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"\n",
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" print('Test: Remove has')\n",
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" trie.remove('has')\n",
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" words_removed = ['a', 'has', 'me', 'mens']\n",
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" words = ['at', 'hat', 'he',\n",
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" 'men', 'met']\n",
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" for word in words:\n",
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" assert_true(trie.find(word) is not None)\n",
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" for word in words_removed:\n",
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" assert_true(trie.find(word) is None)\n",
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"\n",
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" print('Success: test_trie')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestTrie()\n",
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" test.test_trie()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution Notebook\n",
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"\n",
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"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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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.5.0"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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