mikamix

main = print $ sum [x | x <- [1..999], mod x 3 == 0 || mod x 5 == 0]

mikamix

fibs = 1 : 2 : zipWith (+) fibs (tail fibs)

main = print $ sum [x| x <- takeWhile (< 4000000) fibs, even x]

mikamix

primeFactors n = primeFactors' n 2
  where
    primeFactors' n f
      | f ^ 2 > n      = [n]
      | n `mod` f == 0 = f : primeFactors' (n `div` f) f
      | otherwise      = primeFactors' n (f + 1)

main = print $ maximum $ primeFactors 600851475143

mikamix

euler4(Answer) :-
    findall(X, palindromes(X), Palindromes),
    max_list(Palindromes, Answer).

palindromes(Z) :-
    between(100, 999, X),
    between(X, 999, Y),
    Z is X * Y,
    is_palindrome(Z).

mikamix

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

mikamix

main = print $ (sum [1..100] ^ 2) - (sum [x ^ 2| x <- [1..100]])

mikamix

euler7 = primes !! 10000

primes = 2 : 3 : [x| x <- [5, 7..], is_prime x]

is_prime n = is_prime' [3, 5..]
  where
    is_prime' (x : xs)
      | n `mod` x == 0  = False
      | x ^ 2 > n       = True
      | otherwise       = is_prime' xs

mikamix

import Data.Char (digitToInt)

euler8 = maximum $ accumulate $ map digitToInt given

accumulate numbers
  | length numbers < 5 = []
  | otherwise = product (take 5 numbers) : accumulate (drop 1 numbers)

given = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850

mikamix

euler9(Answer) :-
    between(1, 999, A),
    between(A, 999, B),
    C is 1000 - A - B,
    is_pythagorean_triplet(A, B, C),
    Answer is A * B * C.

is_pythagorean_triplet(A, B, C) :-
    A < B, B < C,
    A ^ 2 + B ^ 2 =:= C ^ 2.

mikamix

euler10 = sum $ takeWhile (< 2000000) (2 : 3 : findPrimes [3] 5)

findPrimes primes number
  | isNotPrime = findPrimes primes (number + 2)
  | otherwise  = number : findPrimes (number : primes) (number + 2)
  where
    isNotPrime    = any isModulable [p| p <- primes, p ^ 2 <= number]
    isModulable p = number `mod` p == 0