open Graph.Pack.Digraph

let read_graph filename =

  let string_of_char = String.make 1 in

  let read_int in_ch =
    let is_valid ch = ch >= '0' && ch <= '9' in
    let ioc ch = (int_of_char ch)-(int_of_char '0') in

    let res = ref 0 in
    let tmp = ref '0' in
    try
      while true do
    tmp := (input_char in_ch);
    if (is_valid !tmp) then
      begin
        res := !res * 10 + (ioc !tmp);
      end
    else
      raise Exit;
      done;
      !res;
    with
    Exit -> !res; in

  let in_ch = open_in filename in
  let nb_of_vertex = read_int in_ch in
  let arr_of_vertex = Array.make nb_of_vertex (V.create 0) in
  let graph = create () in
  begin
    for i=0 to (nb_of_vertex-1) do
      arr_of_vertex.(i)<-(V.create i);
      add_vertex graph arr_of_vertex.(i);
    done;
  end;
  try
    while true do
      let f1 = read_int in_ch in
      let f2 = read_int in_ch in
      add_edge graph (arr_of_vertex.(f1)) (arr_of_vertex.(f2));
    done;
    graph;
  with
      End_of_file -> graph;
;;

(* graphe, sommet, tableau de booleens *)
let rec ancentres g x t =
  iter_succ (fun y_->
    let y = (V.label y_) in
    if not t.(y) then
      begin
    t.(y)<-true;
    ancentres g y_ t;
      end;) g x;
;;


let composanteCFC g x_ =

  let rec descendants g x t =
    iter_pred (fun y_ ->
      let y = (V.label y_) in
      if not t.(y) then
    begin
      t.(y)<-true;
      descendants g y_ t;
    end;) g x
  in
  let x = V.label x_ in
  let nb_of_vertex = nb_vertex g in
  let cfc = Queue.create () in
  let td = (Array.create nb_of_vertex false) in (* change 10 to graph len *)
  let ta = (Array.create nb_of_vertex false) in
  td.(x) <- true;
  ta.(x) <- true;
  descendants g x_ ta;
  ancentres g x_ ta;
  for i=1 to nb_of_vertex do
    if  (td.(x) & ta.(x)) then
      Queue.add x cfc;
  done;
  cfc
;;

let g = read_graph "blog.txt";;
let k = composanteCFC g in
let z = Queue.pop k in
z;;