RenderQs.hs

import qualified Data.Set as Set

type Row = Int
type Col = Int

renderSols :: [[(Row, Col)]] -> IO ()
renderSols = mapM_ (putStrLn . renderQs . Set.fromList)
  where
    renderQs queens = unlines $ map renderRow (range maxRow)
      where
        renderRow r = map renderCol (range maxCol)
          where
            renderCol c
              | (r, c) `Set.member` queens = 'Q'
              | otherwise = '-'

    maxRow = 5
    maxCol = 5

    range n = [0..n-1]

solutions :: [[(Row, Col)]]
solutions = replicate 3 [(0, 3), (1, 1), (2, 4), (3, 2), (4, 0)]

main :: IO ()
main = renderSols solutions