"We have profile data for over 2M+ developers" - if so, why do you hire here?

Or some challenge problems on SPOJ (http://www.spoj.com/problems/challenge/)

Please join us at SPOJ (spoj.com) if you are not afraid of programming. Some examples: http://www.spoj.com/problems/TWOSQRS/ (number theory problem), http://www.spoj.com/problems/KPPOLY/ (geometry).

http://bit.ly/13wIW3c the source and some discussion (stackoverflow.com)

Do you use any of them?

Think so. Please let me know if you know more.

Java example: http://ideone.com/HrXrC

SPOX has been built upon the same engine as ideone.com and spoj.pl, but dedicated to teaching in the context of private lessons or regular courses at different levels, starting from beginners to advanced university students.

I like the 4th - unexpected effect.

http://ideone.com/ntqCb - similar example in VB .NET