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From: "isaac2004" <isaac_2004@yahoo.com>
Newsgroups: comp.lang.ada
Subject: Re: Topological Sort Help
Date: 7 Feb 2007 17:19:12 -0800
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the topological sort that i am trying to accomplish from this
structure will follow the algorithm that i have created from
others(its pretty much the same) the problem is im having trouble
setting up the while loop to traverse the array of digraph information

  PROCEDURE Topological_Sort (
         G        : IN     Digraph;
         Result   :    OUT Stackpointer;
         Hascycle :    OUT Boolean) IS

      S : Set;
   BEGIN
 --               WHILE IsEmpty(G) /= False DO
      --                      S  := set of all vertices in V who have
no sucessors
      --                      if S is empty
      --                        hascycle := true;
      --                        return hascycle
      --                        end if
      --                       take the greatest element e in S
      --                      push e onto a stack
      --             remove all edge in E that have e as a destination
      --            remove e from v
      --            end loop

this is the algorithm i have, the while loop makes sure the graph is
not a cycle(if it does that kicks out) if there is no cycle it takes
the vertes with no sucessors and adds it to a stack. is this setup
possible, if so setting up the if statement nested for loops is
throwing me off, i have functions like

  FUNCTION IsStronglyConnected (
         G : Digraph)
     RETURN Boolean IS
      EdgeSet   : Set;
      VertexSet : Set;
   BEGIN
      FOR I IN G'RANGE LOOP
         VertexSet := VertexSet + Character(I);
         FOR J IN G'RANGE LOOP
            IF G(I,J) = True AND I /= J THEN
               EdgeSet := EdgeSet + Character(J);
            END IF;
         END LOOP;
      END LOOP;
      IF VertexSet <= EdgeSet THEN
         RETURN True;
      ELSE
         RETURN False;
      END IF;
   END IsStronglyConnected;

that checks connectivity of the graph and this is the style i have
been using. can i get any help with the top sort. thanks so much any
advice would be great



On Feb 6, 1:06 am, "Ludovic Brenta" <ludo...@ludovic-brenta.org>
wrote:
> On Feb 6, 3:18 am, "isaac2004" wrote:
>
> > "fpund online" is right i know the basics of how it works but
> > implementing anything into it is the part im getting stuck at. any
> > help
>
> It is my policy not to do students' assignments for them. That would
> be a disservice, as the purpose of assignments is to make students
> think and work; that's the only real way of learning. So far, apart
> from searching "online" and asking questions here, you have not shown
> evidence of doing any actual work. I will help you with specific
> questions when you post your program and explain the part you don't
> understand. In the mean time, you would be better advised to ask your
> teacher - it's their job to help you understand the basics.
>
> If you are not a student, my apologies.
>
> --
> Ludovic Brenta.