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

New
jon
Some minor things in the paper edition that says “3 2020” on the title page verso, not mentioned in the book’s errata online: p. 186 But...
New
simonpeter
When I try the command to create a pair of migration files I get an error. user=&gt; (create-migration "guestbook") Execution error (Ill...
New
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
New
rmurray10127
Title: Intuitive Python: docker run… denied error (page 2) Attempted to run the docker command in both CLI and Powershell PS C:\Users\r...
New
brian-m-ops
#book-python-testing-with-pytest-second-edition Hi. Thanks for writing the book. I am just learning so this might just of been an issue ...
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
New
creminology
Skimming ahead, much of the following is explained in Chapter 3, but new readers (like me!) will hit a roadblock in Chapter 2 with their ...
New
tkhobbes
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
New

Other popular topics Top

AstonJ
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
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
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
foxtrottwist
A few weeks ago I started using Warp a terminal written in rust. Though in it’s current state of development there are a few caveats (tab...
New
mafinar
This is going to be a long an frequently posted thread. While talking to a friend of mine who has taken data structure and algorithm cou...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
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
NewsBot
Node.js v22.14.0 has been released. Link: Release 2025-02-11, Version 22.14.0 'Jod' (LTS), @aduh95 · nodejs/node · GitHub
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Sub Categories: