[Haskell-cafe] xkcd #287 "NP-Complete"

[Andrew Coppin]

Albert Y. C. Lai wrote:
> You are right, I saw many solutions but they were all equivalent to 
> just those two. I did not avoid permutation-induced redundancy.
>
> I was unsure how to eliminate that redundancy. After reading your 
> algorithm, I see it. Here is my algorithm modified.

In general, I find this kind of stuff really hard to avoid... :-S

(Or rather, avoid efficiently.)