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kenprice/latticepaths.hs

Created January 1, 2019 23:23
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Project Euler Problem 15
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latticepaths.hs
pascal :: Int -> [Int]
pascal k = iterate pascal' [] !! k
pascal' :: [Int] -> [Int]
pascal' [] = [1]
pascal' xs = [1] ++ zipWith (+) xs (tail xs) ++ [1]
getNumLatticePathsForGrid :: Int -> Int
getNumLatticePathsForGrid n = pascal (n * 2 + 1) !! n
main :: IO()
main = putStrLn (show (getNumLatticePathsForGrid 20))
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