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

brianokken
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...
New
Alexandr
Hi everyone! There is an error on the page 71 in the book “Programming machine learning from coding to depp learning” P. Perrotta. You c...
New
edruder
I thought that there might be interest in using the book with Rails 6.1 and Ruby 2.7.2. I’ll note what I needed to do differently here. ...
New
lirux
Hi Jamis, I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019. This test doesn’t pass for me: ...
New
JohnS
I can’t setup the Rails source code. This happens in a working directory containing multiple (postgres) Rails apps. With: ruby-3.0.0 s...
New
New
adamwoolhether
When trying to generate the protobuf .go file, I receive this error: Unknown flag: --go_opt libprotoc 3.12.3 MacOS 11.3.1 Googling ...
New
leonW
I ran this command after installing the sample application: $ cards add do something --owner Brian And got a file not found error: Fil...
New
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

Other popular topics Top

Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
siddhant3030
I’m thinking of buying a monitor that I can rotate to use as a vertical monitor? Also, I want to know if someone is using it for program...
New
PragmaticBookshelf
From finance to artificial intelligence, genetic algorithms are a powerful tool with a wide array of applications. But you don't need an ...
New
PragmaticBookshelf
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
New
AstonJ
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me. I think the Planck and the Preonic (o...
New
AstonJ
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...
New
Exadra37
Oh just spent so much time on this to discover now that RancherOS is in end of life but Rancher is refusing to mark the Github repo as su...
New
New
CommunityNews
A Brief Review of the Minisforum V3 AMD Tablet. Update: I have created an awesome-minisforum-v3 GitHub repository to list information fo...
New
Fl4m3Ph03n1x
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...
New

Sub Categories: