Algo Q6

AlgoQ6.hs

module Q6 where

import Control.Monad
import Control.Monad.Random
import Data.Numbers.Primes
import Data.List
import Data.Function

thing :: MonadRandom m => Int -> m [Int]
thing n = thing' n
  where
  thing' 0 = return []
  thing' k = do
    rs <- getRandomRs (1,n)
    let pairs = zip [1..k] rs
        collisions = filter ((>= 2) . length)
          . groupBy ((==) `on` snd)
          . sortBy (compare `on` snd)
          $ pairs
    (k :) <$> thing' (length collisions)