leetcode study

This is a repository for a leetcode group study to assist the organizational matter and also to hand over assignments, and also to present sample solution written by myself. I made some effort on the hope that this material is reusable for future use.

Target audience and reasoning

The problem selection and the group study structure is tailored to be challenging for university students in their undergraduate degree which might ot be as fluent as a full time software engineer, but still have basic understanding in data structure and algorithms and also have a solid coding experience in at least one programming language.

The situation might be different between regions, but I feel the education system at least in South Korea and Germany which I have experienced, understandably, doesn't offer to learn how to be competent at leetcode style interviews, as the purpose of studying in the university is not for getting a job in tech industry.

The problem solving skills people can usually pick up and train on their own, but what I think is difficult to train without an industry experience is writing code in a consistent style. That's the reason why we have a separate StyleGuide page to describe which style for each programming language they should follow, as a part of the training.

Group study structure

The owner of this repository will be acting as a tutor, mainly involved in the the assignments handouts and reviewing attendees' solution via github pull requests on a weekly basis. The weekly assignments are selected in a way that attendees would not be able to finish in five hours, so they have to timebox on which problem they will be solving.

This is because unlike regular univesity courses, the activity in this study group is only a voluntary and non evaluative, and I wanted attendees who are already in a competent level to be able to spend enough time practicing, while making everyone else not be overwhelmed and make aware that the weekly assignments are not meant to be solved within five hours. To see how to sumbit your assignments, please go to Assignment submission

Also, after submitting solutions every week we will meet and the attendees will explain their approach of how they solved the problem. I feel that people also get little chance in the university on explaining their technical thoughts to others in a comprehensible manner, which as a regular SWE you grow the skill over time, but is also critical for these kinds of interviews to train them beforehand.

In the very beginning of the course, there will be a level testing session for each attendee with the tutor, to have an idea on the group in general and to plan how to tailor the problems appropriately.

Level testing

There will be a one hour session for the tutor to understand the group, please refer to some sample problems that I put in each study directory (e.g. study0/LevelTest.md). I will ask one or two questions out of the two depending on how the attendees go along with them.

Assignment handout, submission, code review, and discussion session.

Assignment handout

The assignments will be posted in studyX/assignments.md (e.g. study0/assignments.md) every week.

Setup for assignment submission

1. Create a public repository
2. Go to Settings of the repository, go to collborators click Add people and add h-joo.
3. Click 'pending invite' and you will be able to copy the invitation link, send it to the tutor.
4. Create a directory for each week.

Problem Solving

The submission tools in leetcode run and test your code against the visible and hidden test cases. As it's running on a server, they are usually slower than when you run the result on the local machine. Thus, it's better that you have the programming language installed on your local machine for better throughput for testing at least for the visible test cases.

So for the better utilization of your time, please pick up the test cases which are visible through its UI, so test your program with those before your actual attempt to submit it.

Submitting solutions

When you have a valid solution (a solution that passes on leetcode), create a branch for each week of and create a pull request and assign h-joo to the PR whenever you have the solution to the first problem.

Note : You might get errors while trying to add the tutor as a reviewer if you either haven't grant the tutor collaborators permission or I haven't accepted the invite yet.

Follow these steps to structure the file and PR:

1. Create a branch for a submission of a solution for a whole week.
2. Create a directory with a week number (e.g. week0)
3. Create a file following the name of the problem (valid-boomerang) with underscore instead of a hyphen (e.g. week0/valid_boomerang.py)
4. Put a comment at the top of the submitted files, a link to the problem e.g. :

# https://leetcode.com/problems/valid-boomerang/
import math
...

5. Whenever you have a solution for the first problem you solved, open a PR and send it to h-joo.
6. Update new solutions to the same branch. Note: Please do NOT submit everything at once, because this will make me overloaded at the end of a week cycle

Code reviews

The tutor will review the code and leave comments with accordance to code styling and improvements such as simplificiation. Although regular code reviews wouldn't involve in self-conflicting suggestions (deleting a variable vs renaming the same variable), I will do suggest those as this is not actually about making changes, it's about general improvement in the mentees coding style.

Discussion session

We will gather in groups and every attendees will explain their approach and how they solved their problem. This might involve explaining the time or spacial complexity, and I might ask for clarifications if I think the explanation wasn't clear enough.