zaneli

euler1 = sumMultiples 1000 [3, 5]

sumMultiples :: Integral a => a -> [a] -> a
sumMultiples _ []   = 0
sumMultiples n muls = foldl1 (+) [x | x <- [1..(n-1)], any (\y -> x `mod` y == 0) muls]

zaneli

import Data.List
 
euler4 = maxPalindrome 100 999
 
maxPalindrome :: (Enum a, Num a, Ord a, Show a) => a -> a -> a
maxPalindrome n m =
  let list = sortBy (\x y -> compare y x) [x * y | x <- [n..m], y <- [n..m]] in
  head $ filter isPalindrome list
    where
      isPalindrome x = let s = show x in s == reverse s

zaneli

main = print $ prime 10001

prime :: Integral a => Int -> a
prime 1 = 2
prime n = head $ prime' 3 []
  where
    prime' m list | length list >= (n-1) = list
                  | isPrime list         = prime' (m + 2) (m:list)
                  | otherwise            = prime' (m + 2) list
                    where isPrime = all (\x -> m `mod` x /= 0) . dropWhile (\x -> x ^ 2 > m)

zaneli

#!/usr/bin/env perl
use strict;
use warnings;

print "問題1.\n";
my @array = ('Alice', 'Bob');

unshift @array, "Amon2";
push @array, "Catalyst";

zaneli

main = print $ sum $ primes 2000000

primes :: Integral a => a -> [a]
primes n
  | n < 2     = []
  | otherwise = primes' 3 [2] []
    where
      primes' m list list'
        | m > n         = list
        | isPrime list' = primes' (m + 2) (m:list) (list' ++ [m])

zaneli

main = print $ sumHead 10

sumHead :: (Read a, Num a) => Int -> a
sumHead n = read $ take n $ show $ sum nums

nums = [
 37107287533902102798797998220837590246510135740250,
 46376937677490009712648124896970078050417018260538,
 74324986199524741059474233309513058123726617309629,
 91942213363574161572522430563301811072406154908250,

zaneli

import Data.Char

main = print $ digitSum 1000

digitSum :: Integral a => a -> Int
digitSum n = sum $ map digitToInt $ show $ 2 ^ n

zaneli

main = print $ length $ filter (== Sun) firstOfTheMonthWeek

firstOfTheMonthWeek :: [Week]
firstOfTheMonthWeek = firstOfTheMonthWeek' 1900 1 [Mon]
  where
    firstOfTheMonthWeek' 2000 12 ws   = ws
    firstOfTheMonthWeek' y m ws@(w:_) = firstOfTheMonthWeek' y' m' $ ws' (week w $ dayNums y m)
      where
        (y', m') = nextMonth y m
        ws' w | y == 1900 = [w]  -- 1901年からの日曜日の個数を求めたいため、1900年の場合は次の月の曜日だけを再帰の引数に使用する

zaneli

import Data.Char (ord)
import Data.List (sort)
import Text.Regex (matchRegexAll, mkRegex)

main = do names <- readFile "names.txt"
          print $ scoreSum $ sort $ listNames names

-- ダブルクオートで囲まれたカンマ区切りの文字列をリストにする
listNames :: String -> [String]
listNames names = matchNames [] names

zaneli

import Data.Maybe (catMaybes)

data MyType = I Int | F Float | C Char
  deriving (Show)

-- 再帰を使う
filterC :: [MyType] -> [MyType]
filterC []           = []
filterC (x@(C _):xs) = x:filterC xs
filterC (_:xs)       = filterC xs