module Exercise_5 where
{-import Test.QuickCheck-}
import Data.List

{- H5.3 -}
{-WETT-}
type Vertex = Int
type Edge = (Vertex, Vertex)
type Graph = ([Vertex], [Edge])

longestPath :: Graph -> Vertex -> Int

containsEdgeTo _ [] = False
containsEdgeTo v (x:xs) = if (v == snd x) then True else containsEdgeTo v xs

start g = [x | x <- fst g, not (containsEdgeTo x (snd g))] !! 0

longestPath g z = lp (snd g) (start g) z

lPath g s z = undefined


nach e w = [v | (v,w1) <- e, w1 == w]


{- Start s, Knoten v-}
lp e s v = (if (v == s) then 0 else maximum ([(1 + lp e s vn) | vn <- vorgaenger] ++ [-999999999])) where vorgaenger = (nach e v)

{--}

{-TTEW-}
{-
-- generates a DAG with u vertices and only one node without incoming edges
-- you can use this function to test your implementation using QuickCheck
genDag :: Int -> Gen Graph
genDag n = let v = [1..n] in
  do b <- mapM (\i -> choose (1,n-i)) [1..n-1]
     t <- mapM (\(c,i) -> vectorOf c (choose (i+1, n))) (zip b [1..n])
     let e = nub $ ([(1, i) | i<-[2..n]] ++ edges t 1 [])
     return $ (v,e)
  where
    edges [] _ acc = acc
    edges (ts:xs) i acc = edges xs (i+1) (acc ++ [(i,t) | t<-ts])
-}