2GMon

-- Project Euler : Problem 18
--
-- 総当たり回避
-- 三角形をひっくり返して，1つ下のリストに上のリストを足していく

triangle :: [[Int]]
triangle = [
           [75],
           [95, 64],
           [17, 47, 82],

2GMon

import Data.List

-- [a]と[b]の全ての組み合わせをfで計算するzipWithみたいなもの
-- 例: zipWith' (*) [1,2,4,8] [1,3]
--       >> [1,3,2,6,4,12,8,24]
zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWith' _ _ [] = []
zipWith' _ [] _ = []
zipWith' f (a:as) b = (map (f a) b) ++ (zipWith' f as b)

2GMon

-- Project Euler : Problem 19

isBissextile :: Int -> Bool
isBissextile y
    | (y `mod` 400 /= 0) && (y `mod` 100 == 0) = False
    | y `mod` 4 == 0                           = True
    | otherwise                                = False

-- y年m月の日数
daysOfMonth :: Int -> Int -> Int

2GMon

-- Project Euler : Problem 21

import Data.List

-- [a]と[b]の全ての組み合わせをfで計算するzipWithみたいなもの
-- 例: zipWith' (*) [1,2,4,8] [1,3]
-- >> [1,3,2,6,4,12,8,24]
zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWith' _ _ [] = []
zipWith' _ [] _ = []

2GMon

-- Project Euler : Problem 22

import Data.List
import Data.Char
import System.IO

alphabetScore :: Char -> Int
alphabetScore c = ord c - ord 'A' + 1

nameScore :: String -> Int

2GMon

-- Project Euler : Problem 23

import Data.List

-- [a]と[b]の全ての組み合わせをfで計算するzipWithみたいなもの
-- 例: zipWith' (*) [1,2,4,8] [1,3]
-- >> [1,3,2,6,4,12,8,24]
zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWith' _ _ [] = []
zipWith' _ [] _ = []

2GMon

-- Project Euler : Problem 24

-- 10の倍数
multipleOf10 :: Int -> [Int]
multipleOf10 n = zipWith (^) (repeat 10) [0..n]

-- [a]の順列のInt番目
permutaion :: (Eq a) => [a] -> Int -> [a]
permutaion []  _ = []
permutaion [x] _ = [x]

2GMon

-- Project Euler : Problem 25

fibonacci :: [Integer]
fibonacci = 1:fib 1 2
    where fib a b = a:fib b (a + b)

main = print $ fst $ head $ dropWhile (\(x, y) -> y < 1000) $
       map (\(x, y) -> (x, length $ show $ y)) $ zip [1..] fibonacci

-- 4782

2GMon

-- Project Euler : Problem 29

import Data.List

main = print $ length $ map head $ group $ sort [a^b | a <- [2..100], b <- [2..100]]
-- nubよりもmap head $ group の方が速かった

-- 9183
-- ./dailycoding29  0.02s user 0.01s system 92% cpu 0.029 total

2GMon

-- Project Euler : Problem 30

import Data.Char

sumFactorialOf5 :: Int -> Int
sumFactorialOf5 = sum . map (^5) . map digitToInt . show

main = print $ sum [a | a <- [2..9^5*6], a == sumFactorialOf5 a]

-- 443839