Sudoku Puzzle in React (Now built on Netlify: https://competent-aryabhata-ab481d.netlify.app)

UPDATE (11-02-2020) This is a short update mentioning that the sudoku application is now fully dockerized. Please follow the docker.env.example files in the frontend and backend folders for the creation of those environment files and their values.

Docker steps:

1. Install docker desktop
2. run docker-compose up -d --build at the top level
3. Congrats, your docker containers are running! Now you can make changes to the frontend or backend and it will update on the fly.
4. when you want to shut it off, run docker-compose down a) if you want to remove the volumes, use docker-compose down -v, which is useful if you want to change the password for the mongodb instance.

One of the fields in the docker.env.example for the backend is MONGO_INITDB_ROOT_PASSWORD. This password field will set the password to connect to the MongoDB instance. If you need to change the password for any reason, refer to 4a).

UPDATE (10-27-2020)

After a long 2 months, I have now successfully added a save game feature!!! You will now be able to log in to auth0 and access the ability to save, load, overwrite and delete your sudoku games. Please give it a try and feel free to email me at jngchenghin@gmail.com for any issues or comments.

UPDATED (08-27-2020)

Auth0 authentication will be added very soon.

As a warning, DO NOT HIT the back button after logging in to go back to the login screen. You will be met with an Auth0 error that will determine that you are using the system incorrectly.

I have updated the login box for Auth0 to use the newer lightweight version. It has fixed a few of my troubling/extremely frustrating issues with react-router and preventing back button presses (which did not work). It has notably fixed the bug where a user could hit the back button and relogin again with the system not throwing any errors.

UPDATED (05-22-2020)

Instead of the grid being populated through a brute force algorithm, a new backtracking algorithm is used! Link to the source here: https://www.youtube.com/watch?v=G_UYXzGuqvM I modified a little bit of the algorithm in the video by writing a helper function that checks if the filled sudoku grid is a valid solution then break out instead of having the recursive algorithm check for every single solution (since I am using this algorithm with an empty grid, it will take a very long time to find every single solution). Another thing I had done is instead of always setting the order of the array as [1,2,3....9], I utilized the fisher yates algorithm to shuffle these 9 numbers such that we would hopefully get a different ordering each time from the solve function. The shuffle function could perhaps generate 9! different possibilities (9 choices for the first index, then 8, then 7, etc....).

This is my first attempt at creating an app in React. Utilizing several resources from reactjs.org to help understand how to utilize components, props and state to accomplish the task at hand. The basic idea of a Sudoku is as follows:

1. Only one number from 1-9 is allowed on each row
2. Only one number from 1-9 is allowed on each column
3. Only one number from 1-9 is allowed in each grid

The goal of the game is to find the missing numbers in the grid such that all three of these conditions are satisfied and if they are then you have successfully completed the puzzle. If not, then you must backtrack and find out which numbers are inserted incorrectly.