Hello all I am trying to implement depth search in Haskell. My issue here is kind of backtracking. Haskell code for depth first search import Data.List import Data.Array import Control.Monad type Node = Int type Graph = Array Int [ Node ] dfs' :: Graph -> Node -> [ Node ] -> [ Node ] dfs' g v vis = dfsfun lst where lst = g ! v dfsfun [] = vis dfsfun ( x : xs ) | elem x vis = dfsfun xs | otherwise = dfs' g y ( v : vis ) --set the flag true if the graph is direct otherwise false buildGraph :: ( Int , Int ) -> [ ( Node , Node ) ] -> Bool -> Graph buildGraph bnds xs f | f = accumArray ( flip (:) ) [] bnds xs --direct graph a->b | otherwise = accumArray ( flip (:) ) [] bnds xss where --indirect a -> b and b -> a xss = foldr ( \ ( x , y ) b -> ( y , x ) : b ) xs xs dfsSearch :: Graph -> Int -> [ Node ] dfsSearch g v = dfs' g v [] Lets create a indirect graph ghci>let g = buildGraph ( 0 , 5 ) [ ( 0 , 1 ) , ( 0 , 2 ) , ( 0 , 3 ) , ( 0 , 4 ) ] False ghci>g array (0,5) [(0,[4,3,2,1]),(1,[0]),(2,[0]),(3,[0]),(4,[0]),(5,[])] ghci>dfsSearch g 0 [0] Here I am getting only 0 but it should return [ 0 , 1 , 2 , 3 , 4 ] . What is happening here when i am passing 0 as root node to function , at first level i get lst = [ 4 , 3, 2, 1 ] . First element of this list is 4 so 0 is added to vis list and now 4 is passed to dfs' as parent. When it goes down , we get lst = [0] and since 0 is member of vis list so it returns the vis as result . When we write dfs in c/c++ then it returns to calling function and again loops through remaining element which i am not able visualize in Haskell. Could some one please help me how to solve this issue . Regards Mukesh Tiwari