module FrequencyQueries where

import           Debug.Trace
import qualified Data.Map                           as Map
{-
You are given queries. Each query is of the form two integers described below:
- 1:x Insert x in your data structure.
- 2:y Delete one occurence of y from your data structure, if present.
- 3:z Check if any integer is present whose frequency is exactly z. If yes, print 1 else 0.
-}
-- Complete the freqQuery function below.
freqQuery :: [[Int]] -> ([Int], Map.Map Int Int)
freqQuery queries = foldr op ([], Map.empty) queries
  where
    op (1 : [x]) (acc, m) = (acc, Map.insertWith (+) x 1 m)
    op (2 : [y]) (acc, m) = (acc, Map.update clear y m)
    op (3 : [z]) (acc, m) = if (Map.size (Map.filter (== z) m)) > 0
        then (1 : acc, m)
        else (0 : acc, m)
    clear f = if (f - 1) == 0 then Nothing else Just $ f - 1 -- never seems to run

-- run with freqQuery [[1,3],[2,3]]