FLOLAC 2018 0-2

histogram.hs

import Data.List

histogram :: [Int] -> String
histogram = unlines . reverse . putNumber . transpose . mkLines
            where putNumber = ("0123456789" :) . ("==========" :)

mkLines :: [Int] -> [String]
mkLines = graph . group . sort . ([0..9] ++)

graph :: [[Int]] -> [String]
graph = fst . (foldr graph' ([], 0))
        where graph' xs (ys, prevLen) = ((take len (mkStar xs)):ys, len)
                                        where len = max prevLen (length xs)

mkStar :: [Int] -> String
mkStar = (++ repeat ' ') . tail . map (const '*')