Question

I need to write SCC algorithm in standard ML. But I don’t know how.
I have following TYPEs which have to be uesd in the code:

type vertex = int
type edge = int * int
type graph = (vertex * vertex list) list


fun dfs (g: graph) (n: vertex): vertex list = 
  let
    fun helper (todo: vertex list) (visited: vertex list): vertex list =
    case todo of
      [] => []
    | h::t => if (List.exists (fn x => x = h) visited)
                then helper t visited
                else
                  let
                    val adj = case List.find (fn (n, _) => n = h) g of
                                NONE => raise Fail "incomplete adjacency list"
                              | SOME (_, adj) => adj
                  in
                    h :: (helper (adj @ t) (h::visited))
                  end
  in
    helper [n] []
  end

The above code has been compiled and run correctly.
I put these in the code because I know in computing SCC dfs is needed.
Does anyone have a solution?

Answer 1

Pseudo code – http://algowiki.net/wiki/index.php/Tarjan's_algorithm.