16 Jul
2008
16 Jul
'08
9:34 a.m.
apfelmus wrote:
In other words, we have now calculated the more efficient program
euler201 = map snd . filter ((==50) . fst) . subsums $ squares where subsums [] = singleton (0,0) subsums (x:xs) = map (\(n,s) -> (n+1,s+x)) (subsums xs) `union` subsums xs
I forgot something very important, namely that the common subexpression subsums xs has to be shared euler201 = map snd . filter ((==50) . fst) . subsums $ squares where subsums [] = singleton (0,0) subsums (x:xs) = let s = subsums xs in map (\(n,s) -> (n+1,s+x)) s `union`s Otherwise, this exercise would be pointless and the runtime exponential ... :O Regards, apfelmus