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https://github.com/donnemartin/interactive-coding-challenges
synced 2026-01-08 18:38:03 +00:00
Added hash map challenge.
This commit is contained in:
Donne Martin
217
arrays_strings/hash_map/hash_map_challenge.ipynb
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217
arrays_strings/hash_map/hash_map_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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"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges).</i></small>"
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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 hash table with set, get, and remove 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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"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
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"\n",
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"* For simplicity, are the keys integers only?\n",
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" * Yes\n",
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"* For collision resolution, can we use linked lists?\n",
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" * Yes\n",
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"* Do we have to worry about load factors?\n",
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" * No"
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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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"* get on an empty hash table index\n",
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"* set on an empty hash table index\n",
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"* set on a non empty hash table index\n",
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"* set on a key that already exists\n",
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"* remove on a key with an entry\n",
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"* remove on a key without an entry"
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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/coding-challenges/blob/master/arrays_strings/hash_map/hash_map_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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"class Item(object):\n",
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" \n",
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" def __init__(self, key, value):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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"class HashTable(object):\n",
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" \n",
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" def __init__(self, size):\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 hash_function(self, key):\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 set(self, key, value):\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 get(self, key):\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, key):\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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"\n",
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"\n",
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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_hash_map.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestHashMap(object):\n",
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" \n",
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" # TODO: It would be better if we had unit tests for each\n",
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" # method in addition to the following end-to-end test\n",
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" def test_end_to_end(self):\n",
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" hash_table = HashTable(10)\n",
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" \n",
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" print(\"Test: get on an empty hash table index\")\n",
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" assert_equal(hash_table.get(0), None)\n",
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" \n",
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" print(\"Test: set on an empty hash table index\")\n",
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" hash_table.set(0, 'foo')\n",
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" assert_equal(hash_table.get(0), 'foo')\n",
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" hash_table.set(1, 'bar')\n",
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" assert_equal(hash_table.get(1), 'bar')\n",
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" \n",
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" print(\"Test: set on a non empty hash table index\")\n",
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" hash_table.set(10, 'foo2')\n",
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" assert_equal(hash_table.get(0), 'foo')\n",
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" assert_equal(hash_table.get(10), 'foo2')\n",
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" \n",
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" print(\"Test: set on a key that already exists\")\n",
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" hash_table.set(10, 'foo3')\n",
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" assert_equal(hash_table.get(0), 'foo')\n",
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" assert_equal(hash_table.get(10), 'foo3')\n",
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" \n",
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" print(\"Test: remove on a key that already exists\")\n",
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" hash_table.remove(10)\n",
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" assert_equal(hash_table.get(0), 'foo')\n",
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" assert_equal(hash_table.get(10), None)\n",
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" \n",
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" print(\"Test: remove on a key that doesn't exist\")\n",
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" hash_table.remove(-1)\n",
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" \n",
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" print('Success: test_end_to_end')\n",
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"\n",
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"def main():\n",
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" test = TestHashMap()\n",
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" test.test_end_to_end()\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/coding-challenges/blob/master/arrays_strings/hash_map/hash_map_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 2",
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"language": "python",
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"name": "python2"
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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": 2
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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": "ipython2",
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"version": "2.7.10"
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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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