frasette

frasette

A Common-Sense Guide to Data Structures and Algorithms, Second Edition: Are Selection Sort steps wrong? (page 71)

Hi @jaywengrow,

I think the table of Selection Sort shows wrong Max number of steps.
For example, for N = 5 we sould have:

  • Comparsions: 10 + Swaps: 2

and not:

  • Comparsions: 10 + Swaps: 4

In the following code, edit size variable to the number of element you want (5,10,20,40,80), run it to print comparsions and steps, and their sum, for a worst case scenario with a descending order array:
fiddle url: JsFiddle

function selectionSort(array) {
  let comparsions = 0;
  let swaps = 0;
  for(let i = 0; i < array.length - 1; i++) {    
    let lowestNumberIndex = i;
    for(let j = i + 1; j < array.length; j++) {
      if(array[j] < array[lowestNumberIndex]) {
        lowestNumberIndex = j;
      }
      comparsions++;
    }
 
    if(lowestNumberIndex != i) {
      swaps++;
      let temp = array[i];
      array[i] = array[lowestNumberIndex];
      array[lowestNumberIndex] = temp;
    }
  }
  let steps = "Comparsions: " + comparsions + " Swaps: " + swaps;
  console.log(steps);
  return array;
}

// code to create a sample of array size = 5,10,20,40,80
let size    = 80;
let counter = size;
let sample  = new Array(size);

for (i = 0; i < size; i++) {
   sample[i] = counter;
   counter--;
}

console.log(selectionSort(sample))

What do you think? Thanks.

Marked As Solved

jaywengrow

jaywengrow

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

Hi,

This is a really good catch! I think that for Selection Sort, the worst case scenario is still 4 swaps, but you’re right that an array in perfect descending order happens not to be the worst case scenario for Selection Sort.

An array like this: [5, 3, 1, 2, 4] - will still give you 4 swaps in Selection Sort.

I’ll have to clarify this in the next version. Thank you!

-Jay

Where Next?

Popular Pragmatic Bookshelf topics Top

sdmoralesma
Title: Web Development with Clojure, Third Edition - migrations/create not working: p159 When I execute the command: user=&gt; (create-...
New
raul
Page 28: It implements io.ReaderAt on the store type. Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt? ...
New
cro
I am working on the “Your Turn” for chapter one and building out the restart button talked about on page 27. It recommends looking into ...
New
jskubick
I’m under the impression that when the reader gets to page 136 (“View Data with the Database Inspector”), the code SHOULD be able to buil...
New
adamwoolhether
I’m not quite sure what’s going on here, but I’m unable to have to containers successfully complete the Readiness/Liveness checks. I’m im...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
New
Henrai
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
New
a.zampa
@mfazio23 I’m following the indications of the book and arriver ad chapter 10, but the app cannot be compiled due to an error in the Bas...
New
davetron5000
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
New

Other popular topics Top

ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
Rainer
My first contact with Erlang was about 2 years ago when I used RabbitMQ, which is written in Erlang, for my job. This made me curious and...
New
AstonJ
poll poll Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
AstonJ
We have a thread about the keyboards we have, but what about nice keyboards we come across that we want? If you have seen any that look n...
New
PragmaticBookshelf
Tailwind CSS is an exciting new CSS framework that allows you to design your site by composing simple utility classes to create complex e...
New
New
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New
PragmaticBookshelf
Use advanced functional programming principles, practical Domain-Driven Design techniques, and production-ready Elixir code to build scal...
New

Sub Categories: