Created
January 17, 2014 22:03
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import Data.List (nub, group) | |
-- problem 31 | |
isPrime :: Int -> Bool | |
isPrime n = length (filter (\x -> (mod n x) == 0) [2..n-1]) == 0 && n > 1 | |
-- problem 32 | |
pgcd :: Int -> Int -> Int | |
pgcd a 0 = a | |
pgcd a b = pgcd b (mod a b) | |
-- problem 33 | |
coprime :: Int -> Int -> Bool | |
coprime a b = pgcd a b == 1 | |
-- problem 34 | |
totientPhi :: Int -> Int | |
totientPhi n = length $ filter (\x -> x == True) $ map (\x -> coprime n x) [1..n] | |
primes n = [x | x <- [2..n-1], isPrime x] | |
-- problem 35 | |
primeFactor :: Int -> [Int] | |
primeFactor n = reverse $ helper n (reverse $ primes n) [] | |
where helper 1 _ acc = acc | |
helper n [] acc = acc | |
helper n (x:xs) acc = if mod n x == 0 then helper (div n x) xs (acc ++ [x]) else helper n xs acc | |
generatePrimeFactor :: Int -> [Int] -> [Int] -> [Int] | |
generatePrimeFactor 1 _ acc = acc | |
generatePrimeFactor n [] acc = acc | |
generatePrimeFactor n p@(x:xs) acc = if mod n x == 0 then generatePrimeFactor (div n x) p (acc ++ [x]) else generatePrimeFactor n xs acc | |
primeFactorAsc :: Int -> [Int] | |
primeFactorAsc n = nub $ generatePrimeFactor n (primes n) [] | |
-- problem 36 | |
primeFactorAsc' :: Int -> [(Int, Int)] | |
primeFactorAsc' n = map (\x -> (head x, length x)) $ group $ generatePrimeFactor n (primes n) [] | |
-- problem 37 | |
phi :: Int -> Int | |
phi n = foldl (\acc x -> acc * ((fst x) - 1) * (fst x) ^ ((snd x) - 1)) 1 (primeFactorAsc' n) | |
-- problem 39 | |
primesR :: Int -> Int -> [Int] | |
primesR l u = [x | x <- [l..u-1], isPrime x] | |
-- problem 40 | |
goldbach :: Int -> [(Int, Int)] | |
goldbach n = helper (primes n) n | |
where helper [] n = [] | |
helper (x:xs) n = [(x,v2) | v2 <- xs, x + v2 == n] ++ helper xs n | |
oneGoldbach = head . goldbach | |
goldbachList :: Int -> Int -> [(Int, [(Int,Int)])] | |
goldbachList lower upper = map (\x -> (x, goldbach x)) [x | x <- [lower..upper], mod x 2 == 0] | |
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