Online judge

Sometime back I came across Sphere Online Judge (SPOJ). A ‘judge’ is a mechanism through which you can verify your programming solutions.
The SPOJ contains a huge range of programming problems. You need to code a solution in one of the supported languages (from Unix shell scripting to C to Java to esoteric languages like B**fcuk). When you submit the solution, the judge will execute your code with predetermined input and match against predetermined output. If all goes well, your solution will be accepted. Otherwise, it will say ‘compilation error’, or ‘incorrect output’ or ‘time limit exceeded’. It will not tell you the input values or expected output, nor will it tell you the input for which your program is going wrong.

Its very interesting, the problems are very challenging and I gave some problems a try. At the end of it, you can see the report generated by the judge specific to you:

http://www.spoj.pl/users/hardeeps/

Also, you can see the submission history:

http://www.spoj.pl/status/hardeeps/

or, showcase a signed certificate that the judge provides:

http://www.spoj.pl/status/hardeeps/signedlist/

You can see that I have tried various languages, including Java, Bash (Unix shell) and Perl. I am yet to prove my programming skills in C. 🙂

The result AC means that the solution is accepted. The certificate also shows that I was able to calculate PI correctly to 2500 places of decimal in less than 24 seconds – I used the identity described in this blogpost.

I have tried to understand how to verify the digital signature on the certificate but have not been successful. The author informs me that a PHP function is being used to generate the certificate. It would be good if someone can get this working (please post in comments).

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