Awesome

The problem

I saw this problem posted on facebook:

This problem can be solved by pre-school children in 5-10 minutes, by programer - in 1 hour, by people with higher education ... well, check it yourself! :)

8809=6, 7111=0, 2172=0, 6666=4, 1111=0, 3213=0, 7662=2, 9313=1, 0000=4, 2222=0, 3333=0, 5555=0, 8193=3, 8096=5, 7777=0, 9999=4, 7756=1, 6855=3, 9881=5, 5531=0, 2581=?

It took me about an hour to solve because I had to set up unit tests.

How to run

Requirements: node.js, NPM, grunt-cli, and the awesome unit test framework 'buster', which is installed through NPM.

Clone the repository and run a npm install in the root of the project. Then run a npm test, or grunt test. It should pass without any errors.

Now start the program by running a npm start. It will throw you into a REPL where you can solve to problem by typing:

> solve(2581);
2

Oh yeah, btw...Spoiler alert!.

Caveats

• If you want to solve the 0000 problem, you have to parse it in as a string.

Documentation

The project uses YUIDocs that can be generated by running grunt docs. This will create a site with documentation in docs/, which can be served on port 8888 by typing grunt connect:docs. If you want to generate docs on file modification you can run grunt watch:docs.

License

Sort of beerwear license.

You may use it for anything you want. If you like it, and we meet in person, you can buy me a beer, whatever. Oh yeah, don't blame me if your computer catches on fire.

P.S. I love you.