This is not a solved problem by any means. I finished in the top ten, and most competitive teams used a combination of image processing for chad suggestion and brute force. It required hundreds of man hours to reassemble just a handful of documents under controlled conditions.

Imagining a real-life scenario of dozens or hundreds of documents mixed together in a shredder bin makes my head hurt.

So, I wouldn't worry too much about your shredded docs just yet.