@Cmastication I should get on with real work but maybe one big summarising post should focus on just how effin' awesome all these solutions are when they give us one-liners (data.table) or short expressions doing all this in friggin 30 seconds whereas in the original Java contest they have to work rather hard to beat that by large margins.
In short, it is beyond awesome to have a potent data language and with it even competing solutions for every style and preference!