From ac42b882bbdcd269dc13446f0901a7ba5f73a3f4 Mon Sep 17 00:00:00 2001 From: Donne Martin Date: Fri, 3 Jul 2015 19:56:54 -0400 Subject: [PATCH] Added replace char challenge. --- .../replace_char/replace_char_challenge.ipynb | 177 ++++++++++++++++++ .../replace_char/replace_char_solution.ipynb | 68 +++++-- .../replace_char/test_replace_char.py | 29 +++ 3 files changed, 255 insertions(+), 19 deletions(-) create mode 100644 arrays_strings/replace_char/replace_char_challenge.ipynb create mode 100644 arrays_strings/replace_char/test_replace_char.py diff --git a/arrays_strings/replace_char/replace_char_challenge.ipynb b/arrays_strings/replace_char/replace_char_challenge.ipynb new file mode 100644 index 0000000..927416c --- /dev/null +++ b/arrays_strings/replace_char/replace_char_challenge.ipynb @@ -0,0 +1,177 @@ +{ + "cells": [ + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges)." + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "# Challenge Notebook" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Problem: Given a string, replace all spaces with '%20', in-place\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", + "*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n", + "\n", + "* Can we assume the string is ASCII?\n", + " * Yes\n", + " * Note: Unicode strings could require special handling depending on your language\n", + "* Is there enough space in the data structure for this operation?\n", + " * Yes\n", + "* Since Python strings are immutable and we are asked to do this in-place, can I use a bytearray or a list instead?\n", + " * Yes" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Test Cases\n", + "\n", + "* None -> None\n", + "* ' ' -> '%20'\n", + "* ' foo bar ' -> '%20foo%20bar%20'\n", + "* 'foo' -> 'foo'" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Algorithm\n", + "\n", + "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/arrays_strings/replace_char/replace_char_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": [ + "def encode_spaces(string, length):\n", + " # TODO: Implement me\n", + " pass" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "## Unit Test" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "\n", + "\n", + "**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_replace_char.py\n", + "from nose.tools import assert_equal\n", + "\n", + "\n", + "class TestReplace(object):\n", + " \n", + " def test_replace_char(self, func):\n", + " # | are used to satisfy the constraint that\n", + " # there is enough space in the string to\n", + " # replace ' ' with '%20'\n", + " # For each space, add two ||\n", + " str0 = None\n", + " str1 = bytearray(' ||')\n", + " str2 = bytearray(' foo bar ||||||')\n", + " str3 = bytearray('foo')\n", + " func(str0, 0)\n", + " func(str1, 1)\n", + " func(str2, 9)\n", + " func(str3, 3)\n", + " assert_equal(str0, None)\n", + " assert_equal(str1, '%20')\n", + " assert_equal(str2, '%20foo%20bar%20')\n", + " assert_equal(str3, 'foo')\n", + " print('Success: test_replace_char')\n", + "\n", + "def main():\n", + " test = TestReplace()\n", + " test.test_replace_char(encode_spaces)\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/coding-challenges/blob/master/arrays_strings/replace_char/replace_char_solution.ipynb) for a discussion on algorithms and code solutions." + ] + } + ], + "metadata": { + "kernelspec": { + "display_name": "Python 2", + "language": "python", + "name": "python2" + }, + "language_info": { + "codemirror_mode": { + "name": "ipython", + "version": 2 + }, + "file_extension": ".py", + "mimetype": "text/x-python", + "name": "python", + "nbconvert_exporter": "python", + "pygments_lexer": "ipython2", + "version": "2.7.10" + } + }, + "nbformat": 4, + "nbformat_minor": 0 +} diff --git a/arrays_strings/replace_char/replace_char_solution.ipynb b/arrays_strings/replace_char/replace_char_solution.ipynb index cd12f74..e2cdf36 100644 --- a/arrays_strings/replace_char/replace_char_solution.ipynb +++ b/arrays_strings/replace_char/replace_char_solution.ipynb @@ -4,7 +4,14 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes)." + "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges)." + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "# Solution Notebook" ] }, { @@ -18,7 +25,8 @@ "* [Algorithm](#Algorithm)\n", "* [Code](#Code)\n", "* [Pythonic-Code: Not In-Place](#Pythonic-Code:-Not-In-Place)\n", - "* [Unit Test](#Unit-Test)" + "* [Unit Test](#Unit-Test)\n", + "* [Solution Notebook](#Solution-Notebook)" ] }, { @@ -27,12 +35,14 @@ "source": [ "## Constraints\n", "\n", - "*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n", + "*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n", "\n", - "* Can I assume the string is ASCII?\n", + "* Can we assume the string is ASCII?\n", " * Yes\n", " * Note: Unicode strings could require special handling depending on your language\n", "* Is there enough space in the data structure for this operation?\n", + " * Yes\n", + "* Since Python strings are immutable and we are asked to do this in-place, can I use a bytearray or a list instead?\n", " * Yes" ] }, @@ -42,7 +52,7 @@ "source": [ "## Test Cases\n", "\n", - "* NULL->NULL\n", + "* None -> None\n", "* ' ' -> '%20'\n", "* ' foo bar ' -> '%20foo%20bar%20'\n", "* 'foo' -> 'foo'" @@ -54,9 +64,7 @@ "source": [ "## Algorithm\n", "\n", - "Since Python strings are immutable, we'll use a bytearray 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", - "\n", - "![alt text](https://raw.githubusercontent.com/donnemartin/algorithms-data-structures/master/images/replace_string.jpg)\n", + "Since Python strings are immutable, we'll use a bytearray instead to exercise in-place string manipulation as you would get with a C string.\n", "\n", "* Count the number of spaces in the bytearray\n", "* Determine the new bytearray length\n", @@ -125,6 +133,7 @@ "source": [ "import re\n", "\n", + "\n", "def encode_spaces_alt(string):\n", " return re.sub(' ', '%20', string)\n", "\n", @@ -139,13 +148,6 @@ "## Unit Test" ] }, - { - "cell_type": "markdown", - "metadata": {}, - "source": [ - "*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.*" - ] - }, { "cell_type": "code", "execution_count": 3, @@ -157,15 +159,21 @@ "name": "stdout", "output_type": "stream", "text": [ - "Success: test_replace_char\n" + "Overwriting test_replace_char.py\n" ] } ], "source": [ + "%%writefile test_replace_char.py\n", "from nose.tools import assert_equal\n", "\n", - "class Test(object):\n", + "\n", + "class TestReplace(object):\n", + " \n", " def test_replace_char(self, func):\n", + " # | are used to satisfy the constraint that\n", + " # there is enough space in the string to replace\n", + " # ' ' with '%20'\n", " str0 = None\n", " str1 = bytearray(' ||')\n", " str2 = bytearray(' foo bar ||||||')\n", @@ -180,9 +188,31 @@ " assert_equal(str3, 'foo')\n", " print('Success: test_replace_char')\n", "\n", + "def main():\n", + " test = TestReplace()\n", + " test.test_replace_char(encode_spaces)\n", + " \n", "if __name__ == '__main__':\n", - " test = Test()\n", - " test.test_replace_char(encode_spaces)" + " main()" + ] + }, + { + "cell_type": "code", + "execution_count": 4, + "metadata": { + "collapsed": false + }, + "outputs": [ + { + "name": "stdout", + "output_type": "stream", + "text": [ + "Success: test_replace_char\n" + ] + } + ], + "source": [ + "run -i test_replace_char.py" ] } ], diff --git a/arrays_strings/replace_char/test_replace_char.py b/arrays_strings/replace_char/test_replace_char.py new file mode 100644 index 0000000..1d86f66 --- /dev/null +++ b/arrays_strings/replace_char/test_replace_char.py @@ -0,0 +1,29 @@ +from nose.tools import assert_equal + + +class TestReplace(object): + + def test_replace_char(self, func): + # | are used to satisfy the constraint that + # there is enough space in the string to replace + # ' ' with '%20' + str0 = None + str1 = bytearray(' ||') + str2 = bytearray(' foo bar ||||||') + str3 = bytearray('foo') + func(str0, 0) + func(str1, 1) + func(str2, 9) + func(str3, 3) + assert_equal(str0, None) + assert_equal(str1, '%20') + assert_equal(str2, '%20foo%20bar%20') + assert_equal(str3, 'foo') + print('Success: test_replace_char') + +def main(): + test = TestReplace() + test.test_replace_char(encode_spaces) + +if __name__ == '__main__': + main() \ No newline at end of file