[pieguy]

IPSC 2014 problem E looks like a machine learning problem, but the intended solution was to make multiple submissions and use the judge feedback to reverse-engineer the test data. The winning team needed only 6 submissions to hit 95% accuracy. It was one of my favourite problems from the contest.

http://ipsc.ksp.sk/2014/real/problems/e.html

[henrikschroder]

What did they use the sixth submission for? You can win it in five submissions, can't you? :-)