module Bfs where

import qualified Data.Map as M

type Neighs a = a -> [a]

bfs :: Ord k => Neighs k -> [(k, Int)] -> M.Map k Int -> M.Map k Int
bfs f [] visited = visited
bfs f ((q, dist):qs) visited = if new
    then bfs f queue' visited'
    else bfs f qs visited 
    where
        new = M.notMember q visited 
        neighs = f q
        visited' = M.insert q dist visited
        queue' = qs ++ map(,dist+1) neighs