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JavaScript

Marin Leontenko
Marin Leontenko
4,400 Points
Posted by Marin Leontenko
Marin Leontenko
4,400 Points

Hash function - bit rolling

Could someone please solve this and explain: http://185.3.182.78/riddle/index.html

Thanks!

Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

Hi Marin,

Can you give some background on what this is for?

I solved it but it seems like it's part of a test that has to do with applying for a job.

3 Answers

Marin Leontenko
Marin Leontenko
4,400 Points
Marin Leontenko
Marin Leontenko
4,400 Points

You are right, it is a test for job application. I'm sorry if there's a policy against that on these forums. You can contact me privately for details: marin.leontenko@gmail.com

Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

It's not a good idea to get solutions for problems like this because it puts you at a disadvantage. The company is expecting you to be able to solve this on your own. You may be in another situation where you have to solve another problem for them and not in a position to ask for help.

I would suggest that you try to work out the example in the question with pencil and paper to make sure you understand the process. Also, look up javascript's bitwise operators to make sure you understand what each one does.

Good luck!

Marin Leontenko
Marin Leontenko
4,400 Points
Marin Leontenko
Marin Leontenko
4,400 Points

I understand your concerns. Could you al least tell me what level of proficiency in js do i need to solve this (besides bitwise operators). I have some programming experience (Python, Java), but i'm new to javascript.

Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

I don't think you need to know much beyond the bitwise operators.

The question is telling you the steps and operations that you have to take to do a bit roll. That's not something you need to figure out. What I think this question is mostly about is translating those steps into working javascript code.

The example code shown has some errors in it because the programmer didn't correctly translate the steps into code.

If you're completely new to manipulating individual bits then I would practice the different bit operations on some small binary numbers using pencil and paper.

For example, try to figure out why

1011 & 1000 == 1000

This is just a random example and doesn't have anything to do with the problem.

Here's some js code for that example:

var a = 0b1011;
var b = 0b1000;
var result = a & b;
result.toString(2); // "1000" in binary

But I would suggest just working out some different examples on paper and not worrying about the code at first.

Here's a good MDN resource on the different bitwise operators: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators

You only need a few of these operators to solve the problem and these are mentioned in the question itself. However, if they are giving you these types of questions then you'll probably want to learn as much as you can on that page.