mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Add permutations challenge
This commit is contained in:
Donne Martin
parent
ba8325329a
commit
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0
recursion_dynamic/permutations/__init__.py
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0
recursion_dynamic/permutations/__init__.py
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179
recursion_dynamic/permutations/permutations_challenge.ipynb
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179
recursion_dynamic/permutations/permutations_challenge.ipynb
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
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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: Find all permutations of an input 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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"* Can the input have duplicates?\n",
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" * Yes\n",
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"* Can the output have duplicates?\n",
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" * No\n",
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"* Is the output a list of strings?\n",
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" * Yes\n",
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"* Do we have to output the results in sorted order?\n",
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" * No\n",
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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* Can we assume this fits memory?\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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"<pre>\n",
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"* None -> None\n",
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"* '' -> ''\n",
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"* 'AABC' -> ['AABC', 'AACB', 'ABAC', 'ABCA',\n",
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" 'ACAB', 'ACBA', 'BAAC', 'BACA',\n",
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" 'BCAA', 'CAAB', 'CABA', 'CBAA']\n",
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"</pre>"
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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](). If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"class Permutations(object):\n",
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"\n",
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" def find_permutations(self, 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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"**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_permutations.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 TestPermutations(object):\n",
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"\n",
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" def test_permutations(self):\n",
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" permutations = Permutations()\n",
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" assert_equal(permutations.find_permutations(None), None)\n",
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" assert_equal(permutations.find_permutations(''), '')\n",
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" string = 'AABC'\n",
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" expected = [\n",
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" 'AABC', 'AACB', 'ABAC', 'ABCA',\n",
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" 'ACAB', 'ACBA', 'BAAC', 'BACA',\n",
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" 'BCAA', 'CAAB', 'CABA', 'CBAA'\n",
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" ]\n",
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" assert_equal(permutations.find_permutations(string), expected)\n",
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" print('Success: test_permutations')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestPermutations()\n",
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" test.test_permutations()\n",
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"\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]() 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 3",
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"language": "python",
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"name": "python3"
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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": 3
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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": "ipython3",
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"version": "3.5.0"
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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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234
recursion_dynamic/permutations/permutations_solution.ipynb
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234
recursion_dynamic/permutations/permutations_solution.ipynb
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@ -0,0 +1,234 @@
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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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"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
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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: Find all permutations of an input 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)"
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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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"* Can the input have duplicates?\n",
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" * Yes\n",
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"* Can the output have duplicates?\n",
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" * No\n",
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"* Is the output a list of strings?\n",
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" * Yes\n",
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"* Do we have to output the results in sorted order?\n",
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" * No\n",
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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* Can we assume this fits memory?\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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"<pre>\n",
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"* None -> None\n",
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"* '' -> ''\n",
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"* 'AABC' -> ['AABC', 'AACB', 'ABAC', 'ABCA',\n",
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" 'ACAB', 'ACBA', 'BAAC', 'BACA',\n",
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" 'BCAA', 'CAAB', 'CABA', 'CBAA']\n",
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"</pre>"
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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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"* Build a dictionary of {chars: counts} where counts is the number of times each char is found in the input\n",
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"* Loop through each item in the dictionary\n",
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" * If the counts is 0, continue\n",
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" * Decrement the current char's count in the dictionary\n",
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" * Add the current char to the current results\n",
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" * If the current result is the same length as the input, add it to the results\n",
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" * Else, recurse\n",
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" * Backtrack by:\n",
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" * Removing the just added current char from the current results\n",
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" * Incrementing the current char's acount in the dictionary\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(n!) since we are storing the results in an array, or O(n) if we are just printing each result"
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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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"from collections import OrderedDict\n",
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"\n",
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"\n",
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"class Permutations(object):\n",
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"\n",
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" def _build_counts_map(self, string):\n",
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" counts_map = OrderedDict()\n",
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" for char in string:\n",
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" if char in counts_map:\n",
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" counts_map[char] += 1\n",
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" else:\n",
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" counts_map[char] = 1\n",
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" return counts_map\n",
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"\n",
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" def find_permutations(self, string):\n",
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" if string is None or string == '':\n",
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" return string\n",
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" counts_map = self._build_counts_map(string)\n",
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" curr_results = []\n",
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" results = []\n",
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" self._find_permutations(counts_map, curr_results, results, len(string))\n",
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" return results\n",
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"\n",
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" def _find_permutations(self, counts_map, curr_result,\n",
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" results, input_length):\n",
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" for char in counts_map:\n",
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" if counts_map[char] == 0:\n",
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" continue\n",
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" curr_result.append(char)\n",
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" counts_map[char] -= 1\n",
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" if len(curr_result) == input_length:\n",
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" results.append(''.join(curr_result))\n",
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" else:\n",
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" self._find_permutations(counts_map, curr_result,\n",
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" results, input_length)\n",
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" counts_map[char] += 1\n",
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" curr_result.pop()"
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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": 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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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting test_permutations.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_permutations.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 TestPermutations(object):\n",
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"\n",
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" def test_permutations(self):\n",
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" permutations = Permutations()\n",
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" assert_equal(permutations.find_permutations(None), None)\n",
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" assert_equal(permutations.find_permutations(''), '')\n",
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" string = 'AABC'\n",
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" expected = [\n",
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" 'AABC', 'AACB', 'ABAC', 'ABCA',\n",
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" 'ACAB', 'ACBA', 'BAAC', 'BACA',\n",
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" 'BCAA', 'CAAB', 'CABA', 'CBAA'\n",
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" ]\n",
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" assert_equal(permutations.find_permutations(string), expected)\n",
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" print('Success: test_permutations')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestPermutations()\n",
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" test.test_permutations()\n",
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"\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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"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_permutations\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_permutations.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 3",
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"language": "python",
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"name": "python3"
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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": 3
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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": "ipython3",
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"version": "3.5.0"
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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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26
recursion_dynamic/permutations/test_permutations.py
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26
recursion_dynamic/permutations/test_permutations.py
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@ -0,0 +1,26 @@
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from nose.tools import assert_equal
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class TestPermutations(object):
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def test_permutations(self):
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permutations = Permutations()
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assert_equal(permutations.find_permutations(None), None)
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assert_equal(permutations.find_permutations(''), '')
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string = 'AABC'
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expected = [
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'AABC', 'AACB', 'ABAC', 'ABCA',
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'ACAB', 'ACBA', 'BAAC', 'BACA',
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'BCAA', 'CAAB', 'CABA', 'CBAA'
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]
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assert_equal(permutations.find_permutations(string), expected)
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print('Success: test_permutations')
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def main():
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test = TestPermutations()
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test.test_permutations()
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if __name__ == '__main__':
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main()
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