It's a nice strike against software patents though, probably every programmer interested in data structures goes through a whole series of these independent inventions.
To award a patent to someone just because they thought of it first is ridiculous.
I'm no lawyer, but they really need to outlaw patents on 'general purpose' technologies. Adam Carolla famously got sued for owning a podcast company, when someone claimed to have a patent on the entire concept of "downloadable audio". I think there should be a one year jail term for anyone who files a suit about something that ends up being determined "general purpose" technology. Would end the nonsense overnight.
To award a patent to someone just because they thought of it first is ridiculous.