mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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Added compress challenge.
This commit is contained in:
Donne Martin
parent
0c5266a6ad
commit
8b9a1473ea
173
arrays_strings/compress/compress_challenge.ipynb
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173
arrays_strings/compress/compress_challenge.ipynb
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@ -0,0 +1,173 @@
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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: Compress a string such that 'AAABCCDDDD' becomes 'A3B1C2D4'\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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"* Can we assume the string is ASCII?\n",
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" * Yes\n",
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" * Note: Unicode strings could require special handling depending on your language\n",
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"* Can you use additional data structures? \n",
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" * Yes\n",
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"* Is this case sensitive?\n",
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" * Yes\n",
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"* Do you compress even if it doesn't save space?\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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"* None -> None\n",
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"* '' -> ''\n",
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"* 'AABBCC' -> 'AABBCC'\n",
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"* 'AAABCCDDDD' -> 'A3B1C2D4'"
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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/compress/compress_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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"def compress_string(string):\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_compress.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 TestCompress(object):\n",
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" \n",
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" def test_compress(self, func):\n",
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" assert_equal(func(None), None)\n",
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" assert_equal(func(''), '')\n",
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" assert_equal(func('AABBCC'), 'AABBCC')\n",
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" assert_equal(func('AAABCCDDDD'), 'A3B1C2D4')\n",
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" print('Success: test_compress')\n",
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"\n",
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"def main():\n",
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" test = TestCompress()\n",
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" test.test_compress(compress_string)\n",
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" try:\n",
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" test.test_compress(compress_string_alt)\n",
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" except NameError:\n",
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" # Alternate solutions are only defined\n",
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" # in the solutions file\n",
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" pass\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/compress/compress_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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@ -4,7 +4,14 @@
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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://bit.ly/code-notes).</i></small>"
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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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"# Solution Notebook"
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]
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},
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{
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@ -28,9 +35,9 @@
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"source": [
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"## Constraints\n",
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"\n",
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"*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\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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"* Can I assume the string is ASCII?\n",
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"* Can we assume the string is ASCII?\n",
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" * Yes\n",
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" * Note: Unicode strings could require special handling depending on your language\n",
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"* Can you use additional data structures? \n",
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@ -47,9 +54,9 @@
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"source": [
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"## Test Cases\n",
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"\n",
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"* NULL\n",
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"* None -> None\n",
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"* '' -> ''\n",
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"* 'ABC' -> 'ABC'\n",
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"* 'AABBCC' -> 'AABBCC'\n",
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"* 'AAABCCDDDD' -> 'A3B1C2D4'"
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]
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},
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@ -59,9 +66,7 @@
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"source": [
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"## Algorithm: List\n",
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"\n",
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"Since Python strings are immutable, we'll use a list of characters instead to exercise in-place string manipulation as you would get with a C string (which is null terminated, as seen in the diagram below). Python does not use a null-terminator.\n",
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"\n",
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"\n",
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"Since Python strings are immutable, we'll use a list of characters instead to exercise string manipulation as you would get with a C string. We'll convert the list to a string at the end of the algorithm.\n",
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"\n",
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"* Calculate the size of the compressed string\n",
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"* If the compressed string size is >= string size, return string\n",
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@ -79,7 +84,7 @@
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: O(2m) where m is the size of the compressed list and the resulting string copied from the list"
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"* Space: O(n) additional space for the list"
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]
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},
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{
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@ -138,20 +143,15 @@
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"source": [
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"## Algorithm: Byte Array\n",
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"\n",
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"The byte array algorithm similar when using a list, except we will need to work with the bytearray's character codes instead of the characters as we did above when we implemented this solution with a list.\n",
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"As a bonus solution, we can solve this problem with a byte array.\n",
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"\n",
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"The byte array algorithm similar when using a list, except we will need to work with the bytearray's character codes (using the function ord) instead of the characters as we did above when we implemented this solution with a list.\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: O(m) where m is the size of the compressed bytearray"
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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: Byte Array"
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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": 2,
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@ -201,14 +201,14 @@
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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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"## Code: Byte Array"
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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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"*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand. You generally will not be asked to write a unit test like what is shown below.*"
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"## Unit Test"
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]
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},
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{
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@ -217,6 +217,49 @@
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting test_compress.py\n"
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]
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}
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],
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"source": [
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"%%writefile test_compress.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 TestCompress(object):\n",
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" \n",
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" def test_compress(self, func):\n",
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" assert_equal(func(None), None)\n",
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" assert_equal(func(''), '')\n",
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" assert_equal(func('AABBCC'), 'AABBCC')\n",
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" assert_equal(func('AAABCCDDDD'), 'A3B1C2D4')\n",
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" print('Success: test_compress')\n",
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"\n",
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"def main():\n",
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" test = TestCompress()\n",
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" test.test_compress(compress_string)\n",
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" try:\n",
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" test.test_compress(compress_string_alt)\n",
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" except NameError:\n",
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" # Alternate solutions are only defined\n",
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" # in the solutions file\n",
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" pass\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": "code",
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"execution_count": 4,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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@ -228,20 +271,7 @@
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}
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],
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"source": [
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"from nose.tools import assert_equal\n",
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"\n",
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"class Test(object):\n",
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" def test_compress(self, func):\n",
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" assert_equal(func(None), None)\n",
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" assert_equal(func(''), '')\n",
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" assert_equal(func('ABC'), 'ABC')\n",
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" assert_equal(func('AAABCCDDDD'), 'A3B1C2D4')\n",
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" print('Success: test_compress')\n",
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"\n",
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"if __name__ == '__main__':\n",
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" test = Test()\n",
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" test.test_compress(compress_string)\n",
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" test.test_compress(compress_string_alt)"
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"%run -i test_compress.py"
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]
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}
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],
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24
arrays_strings/compress/test_compress.py
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24
arrays_strings/compress/test_compress.py
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@ -0,0 +1,24 @@
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from nose.tools import assert_equal
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class TestCompress(object):
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def test_compress(self, func):
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assert_equal(func(None), None)
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assert_equal(func(''), '')
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assert_equal(func('AABBCC'), 'AABBCC')
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assert_equal(func('AAABCCDDDD'), 'A3B1C2D4')
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print('Success: test_compress')
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def main():
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test = TestCompress()
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test.test_compress(compress_string)
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try:
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test.test_compress(compress_string_alt)
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except NameError:
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# Alternate solutions are only defined
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# in the solutions file
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pass
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if __name__ == '__main__':
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main()
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