Haskell勉強会での成果

日曜日に蛍池で開催されたHaskell勉強会に参加してきました。
Project Eulerの問題を超苦戦しながら解いたのでコードを貼っておきます。

数学苦手すぎる

Problem 1

ts = [3, 6 .. 1000]
fs = [5, 10 .. 999]

sumTwoList :: [Int] -> [Int] -> Int
sumTwoList xs ys = sum xs + sum ys

main = print $ sumTwoList ts fs

Problem 2

problem2 :: Int -> Int
problem2 n = sum $ takeWhile (< n) [x | x <- fibs, x `mod` 2 == 0]
  where
    fibs = 1:1:zipWith(+) fibs (tail fibs)

main = print $ problem2 4000000

Problem 3

-- transribed as sya kyo

primeFactor :: Integer -> Integer -> [Integer]
primeFactor n i
  | n `div` 2 < i  = [n]
  | n `mod` i == 0 = i : primeFactor (div n i) 2
  | otherwise      = primeFactor n $ i + 1

main = print $ primeFactor 600851475143 2

Problem 5

main = print $ foldl lcm 1 [2..20]

Problem 6

xs = [1..100]

main = print $ (-) ((^2) $ sum xs) (sum $ map (^2) xs)