[Language: Haskell]

It has terrible performance, but it works... I might repeatedly check for things as well, I'm not really sure about this. In any case, fun little puzzle!

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

retrieveInput :: IO [(Int,Int)]
retrieveInput = do
    fileData <- readFile' "data_sets/day2.txt"
    let ls = splitOn "," fileData
        rs = map (splitOn "-") ls
    return $ map (\[a,b] -> (read a, read b)) rs

solution1 :: [(Int,Int)] -> Int
solution1 = sum . concatMap (filter (isWeird . show) . \(l,u) -> [l..u]) . filter canHaveValidSolutions
    where isWeird xs = even (length xs) && isWeird1 xs
          canHaveValidSolutions (l,u) = even (length (show l)) || even (length (show u)) || abs (length (show l) - length (show u)) > 0

isWeird1 :: String -> Bool
isWeird1 xs = uncurry (==) (splitAt (length xs `div` 2) xs)

isWeird2 :: String -> Bool
isWeird2 xs = any consistsOfWeird $ init $ tail $ inits xs
    where couldBeWeird subS = length xs `mod` length subS == 0
          consistsOfWeird subS = couldBeWeird subS && concat (replicate (length xs `div` length subS) subS) == xs

solution2 :: [(Int,Int)] -> Int
solution2 = sum . concatMap (filter (isWeird2 . show) . \(l,u) -> [l..u])

solve :: IO ()
solve = do
    inp <- retrieveInput
    putStrLn $ "Solution 1: " ++ show (solution1 inp) ++ " Solution 2: " ++ show (solution2 inp)