PragProg Customers

A Common-Sense Guide to Data Structures and Algorithms, Second Edition: number_of_paths implementations are not equivalent (pg. 176/177)

iwc

iwc

A Common-Sense Guide to Data Structures and Algorithms, Second Edition: number_of_paths implementations are not equivalent (pg. 176/177)

There are two provided implementations for the number_of_paths function. The ‘hardcoded’ version is correct, but the simplified version is not.

pg. 176

def number_of_paths(n):
  return 0 if n <= 0
  return 1 if n == 1
  return 2 if n == 2
  return 4 if n == 3
  return number_of_paths(n - 1) + number_of_paths(n - 2) + number_of_paths(n - 3)
end

pg. 177

def number_of_paths(n):
  return 0 if n < 0
  return 1 if n == 1 || n == 0
  return number_of_paths(n - 1) + number_of_paths(n - 2) + number_of_paths(n - 3)
end

Page 177’s implementation returns 1 instead of 0 for number_of_paths(0).

1 comment
#errata/book-a-common-sense-guide-to-data-structures-and-algorithms-second-edition
0 823 1

First Post!

jaywengrow

jaywengrow

Author of A Common-Sense Guide to Data Structures and Algorithms

Thanks for submitting this. While you are correct that the two methods are not identical in this regard, that is by design. I explain there in the text between the two versions that in the simplified version, we are “rigging” the base case of 0 to return 1 for the very sake of simplifying the code. I hope that helps!

Post #2

Where Next?

View thread on forum
View A Common Sense Guide To Data Structures And Algorithms Second Edition's book portal
Post errata for this book
Post a suggestion for this book
Post a question about this book
Post a review about this book
Home PragProg Customers
#errata/book-a-common-sense-guide-to-data-structures-and-algorithms-second-edition
0 823 1
Last post

Popular Pragmatic Bookshelf topics Top

iPaul
PragProg Customers

The Definitive ANTLR 4 Reference: Program deprecation warning
page 37 ANTLRInputStream input = new ANTLRInputStream(is); as of ANTLR 4 .8 should be: CharStream stream = CharStreams.fromStream(i...
#errata/book-the-definitive-antlr-4-reference
4 987 0
New
brianokken
PragProg Customers

Python Testing with pytest: pytest now requires markers to be declared (downloadable code)
Many tasks_proj/tests directories exist in chapters 2, 3, 5 that have tests that use the custom markers smoke and get, which are not decl...
#errata/book-python-testing-with-pytest
2 1383 2
New
ianwillie
PragProg Customers

Build Websites with Hugo: Code will not run in a working Hugo setup
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
#question/book-build-websites-with-hugo
0 1501 3
New
jeremyhuiskamp
PragProg Customers

Web Development with Clojure, Third Edition (vB17.0): create table syntax invalid
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
#errata/book-web-development-with-clojure-third-edition
0 1835 1
New
jskubick
PragProg Customers

Kotlin and Android Development featuring Jetpack: SwitchCompat's thumbTint and trackTint being ignored (page 76)
I think I might have found a problem involving SwitchCompat, thumbTint, and trackTint. As entered, the SwitchCompat changes color to hol...
#errata/book-kotlin-and-android-development-featuring-jetpack
0 2749 2
New
nicoatridge
PragProg Customers

Kotlin and Android Development: Could not get unknown property ‘kotlin_version’…
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
/book-kotlin-and-android-development-featuring-jetpack
0 8095 6
New
kevinjyh
PragProg Customers

Python Testing with pytest, Second Edition:Abou epub format
Is the book’s epub format available to read on Google Play Books?
#question/book-python-testing-with-pytest-second-edition
0 1126 3
New
AufHe
PragProg Customers

Agile Web Development with Rails 7: page 113 - Seeing the list of products
I’m a newbie to Rails 7 and have hit an issue with the bin/Dev script mentioned on pages 112-113. Iteration A1 - Seeing the list of prod...
#question/book-agile-web-development-with-rails-7
0 2631 9
New
andreheijstek
PragProg Customers

Modern front-end development for Rails, second edition - Struggling to get the first chapter to work
After running /bin/setup, the first error was: The foreman' command exists in these Ruby versions: That was easy to fix: gem install fore...
#errata/book-modern-front-end-development-for-rails
1 1116 3
New
ggerico
PragProg Customers

Programming Machine Learning: some plot files are throwing error
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
#question/book-programming-machine-learning
1 3055 5
New

Other popular topics Top

PragmaticBookshelf
Backend>Learning Resources

Distributed Services with Go
Take your Go skills to the next level by learning how to design, develop, and deploy a distributed service. Start from the bare essential...
pragprog.com
#pragprog/go#published-book/book-distributed-services-with-go
1 4310 0
New
PragmaticBookshelf
Backend>Learning Resources

Programming Machine Learning
Machine learning can be intimidating, with its reliance on math and algorithms that most programmers don't encounter in their regular wor...
pragprog.com
#pragprog#ai/python#published-book/book-programming-machine-learning#math#algorithms
6 5350 3
New
PragmaticBookshelf
Game Dev>Learning Resources

Apple Game Frameworks and Technologies
Design and develop sophisticated 2D games that are as much fun to make as they are to play. From particle effects and pathfinding to soci...
pragprog.com
#pragprog#ios#game-dev#macos/swift#published-book#apple/book-apple-game-frameworks-and-technologies
30 7995 10
New
PragmaticBookshelf
Data Science

Genetic Algorithms in Elixir
From finance to artificial intelligence, genetic algorithms are a powerful tool with a wide array of applications. But you don't need an ...
#pragprog#ai/elixir#published-book/book-genetic-algorithms-in-elixir
25 5243 6
New
AstonJ
Backend>Chat

How to install Ruby 3 with ASDF
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
/ruby#asdf
11 5961 4
New
Maartz
General Dev>Dev Chat

Roc Language - a new purely functional programming language built for speed and ergonomics
Hi folks, I don’t know if I saw this here but, here’s a new programming language, called Roc Reminds me a bit of Elm and thus Haskell. ...
#programminguages#functional-programming
49 5164 14
New
PragmaticBookshelf
General Dev>Learning Resources

A Common-Sense Guide to Data Structures and Algorithms in Python, Volume 1
Big O Notation can make your code faster by orders of magnitude. Get the hands-on info you need to master data structures and algorithms ...
pragprog.com
#pragprog/python#published-book/book-a-common-sense-guide-to-data-structures-and-algorithms-in-python-volume-1
24 5988 11
New
PragmaticBookshelf
Backend>Learning Resources

MySQL 9 Essentials
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
pragprog.com
#pragprog#published-book/mysql/book-mysql-9-essentials
2 4162 0
New
Fl4m3Ph03n1x
AI>Questions

What are the best text-to-speech ai generation tools that you can run locally?
Background Lately I am in a quest to find a good quality TTS ai generation tool to run locally in order to create audio for some videos I...
#ai#text-to-speech
6 12337 3
New
CommunityNews
Game Dev>In The News

Grand Theft Auto: Vice City | DOS games in browser
Open-source implementation of the classic GTA engine now running directly in your browser. Experience the reVC technology demo on DOS.Zon...
dos.zone
#games#browser
0 173 0
New
Back to top

Latest in A Common-Sense Guide to Data Structures and Algorithms, Second Edition

A Common-Sense Guide to Data Structures and Algorithms, Second Edition Portal ❯

PragProg Customers

Pragmatic Bookshelf PragProg Customers ❯

Latest on Devtalk

Devtalk ❯

We ❤️ helpful members!

We reward our most helpful members via our MOTM scheme - by giving away a whopping 25 books per year!

Member of the Month

Devtalk Sponsors

Pragmatic Bookshelf

Practical resources that improve the lives of professional developers.

Erlang Solutions

We build trusted fault-tolerant systems that scale to billions of users.

Honeybadger

Real-time error tracking, performance insights, and observability for devs.

EEF

Supporting innovation across the BEAM ecosystem.

coders51

We build reliable cloud platforms for business-critical systems.

Manning Publications

Develop your skills with books, videos, and courses.

AppSignal

Catch errors, track performance, monitor hosts and more.

WyeWorks

Enabling companies to succeed by building software people love.

Pragmatic Studio

Courses that move you from confusion to "Aha, now I get it!"

Linux New Media

Publishing Linux Magazine, ADMIN, and MakerSpace for 25+ years.

View all our sponsors ❯

Categories:

Sub Categories:

Popular Portals

Devtalk Sponsors

Pragmatic Bookshelf

Practical resources that improve the lives of professional developers.

Erlang Solutions

We build trusted fault-tolerant systems that scale to billions of users.

Honeybadger

Real-time error tracking, performance insights, and observability for devs.

EEF

Supporting innovation across the BEAM ecosystem.

coders51

We build reliable cloud platforms for business-critical systems.

Manning Publications

Develop your skills with books, videos, and courses.

AppSignal

Catch errors, track performance, monitor hosts and more.

WyeWorks

Enabling companies to succeed by building software people love.

Pragmatic Studio

Courses that move you from confusion to "Aha, now I get it!"

Linux New Media

Publishing Linux Magazine, ADMIN, and MakerSpace for 25+ years.

View all our sponsors ❯

We're in Beta

About us Mission Statement See our Roadmap