mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Removed replace char challenge, needs some more work to translate this classic problem to python.
This commit is contained in:
Donne Martin
parent
f7f9160ba4
commit
e75e128aa5
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@ -34,7 +34,6 @@ Continually updated Python Notebooks containing TDD-based coding challenges and
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| [unique_chars](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/unique_chars/unique_chars_solution.ipynb) | Determine if a string contains unique characters |
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| [reverse_string](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) | Reverse characters in a string |
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| [permutation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/permutation/permutation_solution.ipynb) | Determine if a string is a permutation of another |
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| [replace_char](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/replace_char/replace_char_solution.ipynb) | Encode spaces in a string in-place |
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| [compress](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/compress/compress_solution.ipynb) | Compress a string |
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| [rotation](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/rotation/rotation_solution.ipynb) | Determine if a string is a rotation of another |
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| [hash-map](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb) | Implement a hash table with set, get, and remove methods |
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@ -1,177 +0,0 @@
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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/interactive-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: Given a string (a list of characters), replace all spaces with '%20', in-place\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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"* Is there enough space in the data structure for this operation?\n",
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" * Yes\n",
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"* Since Python strings are immutable and we are asked to do this in-place, can I use a bytearray or a list instead?\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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"* None -> None\n",
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"* ' ' -> '%20'\n",
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"* ' foo bar ' -> '%20foo%20bar%20'\n",
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"* 'foo' -> 'foo'"
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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/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."
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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 encode_spaces(string, length):\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_replace_char.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 TestReplace(object):\n",
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" \n",
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" def test_replace_char(self, func):\n",
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" # | are used to satisfy the constraint that\n",
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" # there is enough space in the string to\n",
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" # replace ' ' with '%20'\n",
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" # For each space, add two ||\n",
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" str0 = None\n",
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" str1 = bytearray(' ||')\n",
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" str2 = bytearray(' foo bar ||||||')\n",
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" str3 = bytearray('foo')\n",
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" func(str0, 0)\n",
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" func(str1, 1)\n",
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" func(str2, 9)\n",
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" func(str3, 3)\n",
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" assert_equal(str0, None)\n",
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" assert_equal(str1, '%20')\n",
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" assert_equal(str2, '%20foo%20bar%20')\n",
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" assert_equal(str3, 'foo')\n",
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" print('Success: test_replace_char')\n",
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"\n",
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"def main():\n",
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" test = TestReplace()\n",
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" test.test_replace_char(encode_spaces)\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/arrays_strings/replace_char/replace_char_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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@ -1,240 +0,0 @@
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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/interactive-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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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Given a string (a list of characters), replace in-place all spaces with '%20'\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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"* [Pythonic-Code: Not In-Place](#Pythonic-Code:-Not-In-Place)\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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"* Is there enough space in the data structure for this operation?\n",
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" * Yes\n",
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"* Since Python strings are immutable and we are asked to do this in-place, can I use a list or a bytearray instead?\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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"* None -> None\n",
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"* ' ' -> '%20'\n",
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"* ' foo bar ' -> '%20foo%20bar%20'\n",
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"* 'foo' -> 'foo'"
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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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"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",
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"\n",
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"* Count the number of spaces in the bytearray\n",
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"* Determine the new bytearray length\n",
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"* For each character code in the bytearray, starting from the end of the string\n",
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" * If the character code is a space\n",
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" * bytearray[new length] = '0',\n",
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" * bytearray[new length - 1] = '2',\n",
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" * bytearray[new length - 2] = '%',\n",
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" * new length -= 3\n",
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" * Else\n",
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" * bytearray[new length] = character code,\n",
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" * new length -= 1\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: In-place"
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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": 1,
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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 encode_spaces(string, length):\n",
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" if string is None:\n",
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" return\n",
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" num_spaces = string.count(' ')\n",
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" new_length = length + 2 * num_spaces - 1\n",
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" for i in xrange(length-1, -1, -1):\n",
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" if chr(string[i]) == ' ':\n",
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" string[new_length] = '0'\n",
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" string[new_length-1] = '2'\n",
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" string[new_length-2] = '%'\n",
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" new_length -= 3\n",
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" else:\n",
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" string[new_length] = string[i]\n",
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" new_length -= 1"
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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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"## Pythonic-Code: Not In-Place\n",
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"\n",
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"The following code is Pythonic, but requires using additional data structures as Python strings are immutable. You could use a bytearray or a list instead of a string to simulate manipulating an array of characters."
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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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"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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"import re\n",
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"\n",
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"\n",
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"def encode_spaces_alt(string):\n",
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" return re.sub(' ', '%20', string)\n",
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"\n",
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"def encode_spaces_alt2(string):\n",
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" return string.replace(' ', '%20')"
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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": "code",
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"execution_count": 3,
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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_replace_char.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_replace_char.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 TestReplace(object):\n",
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" \n",
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" def test_replace_char(self, func):\n",
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" # | are used to satisfy the constraint that\n",
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" # there is enough space in the string to replace\n",
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" # ' ' with '%20'\n",
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" str0 = None\n",
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" str1 = bytearray(' ||')\n",
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" str2 = bytearray(' foo bar ||||||')\n",
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" str3 = bytearray('foo')\n",
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" func(str0, 0)\n",
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" func(str1, 1)\n",
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" func(str2, 9)\n",
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" func(str3, 3)\n",
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" assert_equal(str0, None)\n",
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" assert_equal(str1, '%20')\n",
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" assert_equal(str2, '%20foo%20bar%20')\n",
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" assert_equal(str3, 'foo')\n",
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" print('Success: test_replace_char')\n",
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"\n",
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"def main():\n",
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" test = TestReplace()\n",
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" test.test_replace_char(encode_spaces)\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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"output_type": "stream",
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"text": [
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"Success: test_replace_char\n"
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]
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}
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],
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"source": [
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"run -i test_replace_char.py"
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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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@ -1,29 +0,0 @@
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from nose.tools import assert_equal
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class TestReplace(object):
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def test_replace_char(self, func):
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# | are used to satisfy the constraint that
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# there is enough space in the string to replace
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# ' ' with '%20'
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str0 = None
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str1 = bytearray(' ||')
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str2 = bytearray(' foo bar ||||||')
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str3 = bytearray('foo')
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func(str0, 0)
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func(str1, 1)
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func(str2, 9)
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func(str3, 3)
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assert_equal(str0, None)
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assert_equal(str1, '%20')
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assert_equal(str2, '%20foo%20bar%20')
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assert_equal(str3, 'foo')
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print('Success: test_replace_char')
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def main():
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test = TestReplace()
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test.test_replace_char(encode_spaces)
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if __name__ == '__main__':
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main()
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Block a user