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https://github.com/donnemartin/interactive-coding-challenges.git
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Added permutation challenge.
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Donne Martin
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0f34948626
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fb7de503af
171
arrays_strings/permutation/permutation_challenge.ipynb
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171
arrays_strings/permutation/permutation_challenge.ipynb
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@ -0,0 +1,171 @@
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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: Determine if a string is a permutation of another string\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 whitespace important?\n",
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" * Yes\n",
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"* Is this case sensitive? 'Nib', 'bin' is not a match?\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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"* One or more empty strings -> False\n",
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"* 'Nib', 'bin' -> False\n",
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"* 'act', 'cat' -> True\n",
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"* 'a ct', 'ca t' -> True"
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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/permutation/permutation_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 permutations(str1, str2):\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_permutation_solution.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 TestPermutation(object):\n",
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" \n",
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" def test_permutation(self, func):\n",
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" assert_equal(func('', 'foo'), False)\n",
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" assert_equal(func('Nib', 'bin'), False)\n",
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" assert_equal(func('act', 'cat'), True)\n",
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" assert_equal(func('a ct', 'ca t'), True)\n",
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" print('Success: test_permutation')\n",
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"\n",
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"def main():\n",
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" test = TestPermutation()\n",
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" test.test_permutation(permutations)\n",
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" try:\n",
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" test.test_permutation(permutations_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/permutation/permutation_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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"* Is whitespace important?\n",
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@ -110,7 +117,7 @@
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"Notes:\n",
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"* Since the characters are in ASCII, we could potentially use an array of size 128 (or 256 for extended ASCII), where each array index is equivalent to an ASCII value\n",
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"* Instead of using two hash maps, you could use one hash map and increment character values based on the first string and decrement based on the second string\n",
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"* You can short circuit if the lengths of each string are not equal, len() in Python is generally O(1)\n",
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"* You can short circuit if the lengths of each string are not equal, although len() in Python is generally O(1) unlike other languages like C where getting the length of a string is O(n)\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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@ -134,6 +141,7 @@
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"source": [
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"from collections import defaultdict\n",
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"\n",
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"\n",
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"def unique_counts(string):\n",
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" dict_chars = defaultdict(int)\n",
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" for char in string:\n",
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@ -156,15 +164,51 @@
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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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"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_permutation_solution.py\n"
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]
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}
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],
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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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"%%writefile test_permutation_solution.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 TestPermutation(object):\n",
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" \n",
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" def test_permutation(self, func):\n",
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" assert_equal(func('', 'foo'), False)\n",
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" assert_equal(func('Nib', 'bin'), False)\n",
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" assert_equal(func('act', 'cat'), True)\n",
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" assert_equal(func('a ct', 'ca t'), True)\n",
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" print('Success: test_permutation')\n",
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"\n",
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"def main():\n",
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" test = TestPermutation()\n",
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" test.test_permutation(permutations)\n",
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" try:\n",
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" test.test_permutation(permutations_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": 3,
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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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@ -179,20 +223,7 @@
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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_permutation(self, func):\n",
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" assert_equal(func('', 'foo'), False)\n",
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" assert_equal(func('Nib', 'bin'), False)\n",
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" assert_equal(func('act', 'cat'), True)\n",
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" assert_equal(func('a ct', 'ca t'), True)\n",
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" print('Success: test_permutation')\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_permutation(permutations)\n",
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" test.test_permutation(permutations_alt)"
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"run -i test_permutation_solution.py"
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]
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}
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],
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24
arrays_strings/permutation/test_permutation_solution.py
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24
arrays_strings/permutation/test_permutation_solution.py
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from nose.tools import assert_equal
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class TestPermutation(object):
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def test_permutation(self, func):
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assert_equal(func('', 'foo'), False)
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assert_equal(func('Nib', 'bin'), False)
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assert_equal(func('act', 'cat'), True)
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assert_equal(func('a ct', 'ca t'), True)
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print('Success: test_permutation')
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def main():
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test = TestPermutation()
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test.test_permutation(permutations)
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try:
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test.test_permutation(permutations_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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