voting.hs

import Data.List

votes :: [String]
votes = ["Red", "Blue", "Green", "Blue", "Blue", "Red"]

count :: Eq a => a -> [a] -> Int
count x = length . filter (== x)

rmdups :: Eq a => [a] -> [a]
rmdups [] = []
rmdups (x:xs) = x : rmdups (filter (/= x) xs)

result :: Ord a => [a] -> [(Int, a)]
result vs = sort [(count v vs, v) | v <- rmdups vs]

winner :: Ord a => [a] -> a
winner = snd . last . result

ballots :: [[String]]
ballots =
  [ ["Red", "Green"]
  , ["Blue"]
  , ["Green", "Red", "Blue"]
  , ["Blue", "Green", "Red"]
  , ["Green"]
  ]

rmemtpy :: Eq a => [[a]] -> [[a]]
rmemtpy = filter (/= [])

elim :: Eq a => a -> [[a]] -> [[a]]
elim x = map (filter (/= x))

rank :: Ord a => [[a]] -> [a]
rank = map snd . result . map head

winner' :: Ord a => [[a]] -> a
winner' bs =
  case rank (rmemtpy bs) of
    [c] -> c
    (c:cs) -> winner' (elim c bs)