User talk:Gaaijz: Difference between revisions

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Two different approaches with Haskell for the zigzag task.

flist = map (:[])

elist = ~~flip replicate~~ []

elist = cycle [[]]

revNrev True = cycle [reverse,id]

revNrev _ = cycle [id,reverse]

transpN True = id

transpN _ = transpose

zigzag m n = ~~(transpN rev)~~.map concat. transpose

zigzag m n = transpose. map concat. transpose

. uncurry ((.(map (liftM2 (++) (elist.(~~dl-~~).length) flist))).(++~~).(map (liftM2 (++) flist (elist.(dl-).length)))~~)

. uncurry ((.(map (liftM2 (++) ((`take`elist).(`subtract`n).length) flist))).(++)

.(map (liftM2 (++) flist ((`take`elist).(`subtract`n).length))))

$ splitAt k revcs

where

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dl = min m n

nd = abs (m-n)

antiDiags = unfoldr (\((c:cs),xs) -> if null xs then Nothing else Just (take c xs,(cs,drop c xs)))

rev = m<n

([1..dl]++(replicate nd dl)++[dl-1,dl-2..0], [0..m*n-1])

~~pseudoAntiDiags~~ = unfoldr (\((c:cs),xs) -> if null xs then Nothing else Just (take c xs,(cs,drop c xs)))

revcs = zipWith id (cycle [id,reverse]) antiDiags

([1..dl]++(replicate nd dl)++[dl-1,dl-2..0],[0..m*n-1])

:Slower version, almost complete emulation of the J-solution

revcs = zipWith id (~~revNrev~~ ~~rev~~) ~~pseudoAntiDiags~~

-- ~~slower~~, almost complete emulation of the J-solution

groupon f x y= f x == f y

tab n = fst . until (null.snd) (\(xs,ys)-> (xs++[take n ys], drop n ys)) . (,) []

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where fdiag = map (map snd). groupBy (groupon fst).sortBy (comparing fst)

$ zip (map sum $ sequence [[0..m-1],[0..n-1]] ) [0..]

*Main> sum.map sum $ zigzag 500 500

1185103928