DEV Community: Chethana Gopinath

Thanks so much DEV team!

Chethana Gopinath — Fri, 13 Nov 2020 05:57:32 +0000

Today, I got these really cool stickers in my mail as a thank-you gift for leaving a review on the DevDiscuss!!

Felt really happy cause I was having a depressing day, thank you so much for such heart-warming and cool stickers! 💜

How to list Open Source work on resume?

Chethana Gopinath — Thu, 29 Oct 2020 23:43:26 +0000

Hey you wonderful people! :)

So I've noticed that my profile is a bit different, in the sense that I try contributing more to issues(at my own pace) but I do not have impressive side-projects.

They are tiny UI fixes, changes to Rails models and stuff like that, I was wondering if it was worth creating a new section on my resume and mentioning my contributions and limit the number of side-projects to one as I seem to spend more time trying to find issues/repos and work on them rather than work on personal projects.

Would be great if any of you folks could weigh in!

Thanks in advance.

I did it!

Chethana Gopinath — Wed, 28 Oct 2020 01:33:15 +0000

Hello fellow devs,

There is no feeling to describe my emotions when my 4th PR was merged today. This is my first time participating in Hacktoberfest, and my first time not being scared and seeing something through to the end.

My contributions were as follows

Fixing up the alignment on the Sign In page:
https://github.com/ck3g/homebugh/pull/93
Removing extra pagination:
https://github.com/publiclab/mapknitter/pull/1452
Added a field to admin interface:
https://github.com/mrysav/geneac/pull/43
Wrote tester functions within a rake task:
https://github.com/mrysav/geneac/pull/44

Lessons learnt

Always read through the README.md and CONTRIBUTING.md.The first PR was my toughest one. Even though it was a really simple UI fix, since I missed to follow a couple of steps on the README.md, I got into a lot of trouble in terms of setting up the environment.

If you are stuck, you need only ask. Putting this into my head took me ages - I usually suffer in silence and try to work my way out of things by myself, but sometimes, you just gotta get some help. A couple of months ago, I ended up giving up on an issue because of this same reason.

The opensource community is very inviting and nurturing. This is exactly the reason why I was able to finish all my PRs.

A couple of lessons for my Ruby on Rails friends here

rake routes is your forever friend.
Always be careful when setting up the DB part of your app(whether it is MySQL or PostGRES or anything else. It is also helpful to look up Docker.
Always take a look at your Gemfile and also when you start working with an issue, if there's a gem involved, take a look at the documentation of the gem. This will save you a lot of time!

To the rest of you who are working on the challenge, you got it. There's still time and even if you don't finish, you can always work on it next month. After all, there shouldn't be one single month that we should set aside for contributing to open source!

How to connect Docker MySQL image to existing Rails app?

Chethana Gopinath — Sat, 03 Oct 2020 08:08:16 +0000

Greetings fellow devs,

Relatively new to Rails, but so far I have never had weird issues like this. I was having a lot of configuration issues while trying to do a bundle install on existing Rails apps. And brew install mysql did not help so I decided to create a container for mysql alone and use it for an existing Rails app.

These are what I have done so far
1) Created a docker container with MySQL image.
2) Went into my container to see if it connects to mysql commandline within it.
3) Tried running bundle install again but this shows up.

4) Tried to change my database.yml as such

default: &default
  ...Other settings...
  adapter: mysql2
  host: mysql
  port: 3306

where mysql is the container name. Did not work.
5) I also read about Dockerfile and Docker compose - got extremely confused with the whole thing. I have just a single MySQL container that I would like to connect to my Rails app.

So, I'm here right now, frustrated for two days since the beginning of Hacktoberfest unable to run my Rails apps locally to start making contributions.
I don't know where to go with this and how to fix this issue.
Please help.

EDIT - Oct 7 '20
I had also asked about this in here and I got some pretty cool answers!

Solution
Always make sure to have mysql installed on your local, cause when installing the mysql2 gem using bundle install, the bundler would look for mysql developmental headers that are in the same space as the Rails app workspace. Unless your mysql docker image and the rails app run on the same space, you will always get an error. And it won't help even if you bind the port no of localhost to your docker image port on your database.yml cause you are just running bundle install, you are not running any code within the app. This is my explanation from what I read and understood. Hope it helps!

What are some of the things you wish you knew starting out as a full-stack developer?

Chethana Gopinath — Mon, 07 Sep 2020 18:23:21 +0000

Greetings everybody!

Full-stack development is a sea and it's so easy to get lost. It would be great to hear from all full-stack developers in the community. This would help newbies such as myself who are looking to get into full-stack development!
Thanks again! :)

Finding the duplicate number - Leetcode #287 - Python

Chethana Gopinath — Wed, 02 Sep 2020 02:03:07 +0000

Greetings fellow devs!

Hope you're doing well despite the whole pandemic situation and are staying healthy.

I wanted to write about this very interesting/difficult solution to a problem that I learned today.

Finding the duplicate number within an array/list.

Before anything, I would encourage you to take a look at the Leetcode problem statement.

And try to solve it. Doesn't matter if you can't do it. This is an extremely strange problem.

The given

The list of nums contains n+1 integers.
And each num within nums is of range, 1..n(inclusive).
There is only one duplicate number in the list.

Different solutions

Iterate through the list and sort it, and then find if two adjacent nums are equal and return one of those nums.
Store the seen nums in another list, and then return num if the num is already in seen.

Also, follow up note to the problem

Space complexity should be O(1) - constant space.
Time complexity should be less than O(n^2).

Whew, okay. On to the solutions that match the follow-up note.

I did see binary search being listed as a solution, probably to reduce time complexity by half(so O(log n)) with constant space complexity. But I was more interested in another solution and that was a bit challenging. Somehow, it took me about a day to understand this.

nums = [2,6,4,1,3,1,5]
Output - 1

The idea is to have two pointers - slow and fast. These would move through the list by using the current number as the index to the next element to iterate through. And as always, fast moves two steps ahead of slow. The iterations would create a linked list that contains a cycle due to the duplicate element.

So, this problem is being transformed into the problem of finding a cycle within a linked list.

The new problem statement
Given a linked list, find the entrance node/ element of the cycle.

Why should we find the starting point of the cycle?

Read on.

Constructing our linked list
We would now find the sequence of numbers by iterating through nums(given above) and creating a linked list. The duplicate would have the same value and link back to the original value thus creating the cycle. The explanation of how each next number is identified is mentioned in () next to the number.

[2,6,4,1,3,1,5]

You start from the first element.

2 -> 4(nums[2]) -> 3(nums[4]) -> 1(nums[3]) -> 6(nums[1]) -> 5(nums[6]) -> 1(nums[5]) -> 6(nums[1]) -> 5(nums[6]) -> 1(nums[5]) -> ....

And that sequence just goes on. That's a cycle. When we see that, we would be like, damn, now where does that cycle start!?

Okay, fine, let's first construct a visual aid of a linked list from this.

Thanks to Leetcode, we have it here.

Now for the approach

The duplicate element is the entrance of a cycle present within the list of numbers. Wait, whaaaat?

Two steps

Find if there's a loop - while iterating through the list, if at some point, both the slow and fast pointers are pointing to the same node, then yes, a loop is present. Since fast is moving two nodes ahead, fast and slow would point to the same node only if there is a loop.
Find the starting node of the cycle.

How do we do this?
Also, since we found an node where both fast and slow point to, couldn't we just return that?

Well, no.

Why?
The intersection node is not necessarily the duplicate element/node as this intersection node is a node in the cycle where the fast caught up with the slow or where the fast and slow pointers randomly met - this just proves that there's a cycle in the linked list.

To get the exact duplicate element, we need to see where this loop/cycle originated.

To find this origin, we need to push the slow pointer to the start of the list and move both fast and slow pointers at the same rate, one at a time, and when they now meet at the same node, that is the start of the cycle/loop.

Some math-ish stuff
Assuming D = the number of steps/distance from the start of the linked list to the start of the cycle and K = the number of steps/distance from the start of the cycle to the intersection point we determined in Step 1. Since slow moves to the start(0), its position after D steps is D. The fast pointer continues from the intersection point, so its position after D steps would be, nC(some number of cycles) - K, which is equal to D => nC - K = D.

Now, we got that cleared away, time to finally code this up!

class Solution:
    def findDuplicate(self, nums: List[int]) -> int:     
        slow = nums[0]
        fast = nums[0]
        while True:
            slow = nums[slow]
            fast = nums[nums[fast]]
            if slow == fast:
                break    
        slow = nums[0]
        while slow != fast:
            slow = nums[slow]
            fast = nums[fast]   
        return fast

Resources to go through if you're stuck during the struggle of understanding this solution

Gaurav Sen's awesome video on finding the start of the cycle in the linked list. Watch this at least twice and you'll understand.
Floyd's cycle detection algorithm on Wikipedia.
This really cool solution.
Nick White's video to understand that even cool YouTubers struggle with this problem.
Also, it's very important to understand the difference between finding whether a cycle/loop exists in the linked list and finding where the entry/starting node of the cycle is.
Also, this StackOverflow answer is the source of a lot of answers to the questions during the learning process.
Of course, look at the Leetcode solution explanation.

Thank you so much for reading. This solution to the problem was a tough one to understand, soo, if you are stuck in the learning process (I was too!), do let me know, maybe I can help.

Hi!

Chethana Gopinath — Mon, 10 Aug 2020 01:52:03 +0000

Hey everybody!
I'm Chethana and I'm a CS grad student. I just heard of this amazing community and wanted to join you all. I have recently started out on a journey as a problem-solver, which I am extremely passionate about. Very excited to be here and want to learn as much as my brain allows me, every day. I also love to bake, sing and write(I used to have my own blog, but it's been a year since I wrote in it, maybe I should start it up again). I am going to share everything that I learn while solving problems as a beginner and every other interesting things in tech that I come across. I would be really happy if any of my future posts add value to a reader in any small way. Thanks for reading and take care :)!