/**
      * Vypise topologicke usporadani acyklickeho grafu
      * @param graph graf
      */
     public static void orderTopologically(GraphIface graph){
         //Stavy jednotlivych uzlu
         List<Integer> roots = new ArrayList<Integer>();
         for(int i = 0; i < graph.getVertexCount(); i++){
             //pokud nema v puvodnim grafu potomky, tak je korenem 
             //v opacne orientovanem grafu
             if(graph.getEdges(i).size() == 0) roots.add(i);
         }
         GraphIface inverted = graph.inverse(); //vytvor opacne orientovany graf
         int[] state = new int[inverted.getVertexCount()];
 
         for(int i = 0; i < state.length; i++) state[i] = FRESH;
         for(Integer i : roots){
             doOrdering(inverted, i, state);
         }
     }
     /**
      * Provadi samotne usporadani grafu
      * @param graph graf
      * @param vertexNr cislo aktualniho uzlu
      * @param state pole stavu
      */
     private static void doOrdering(GraphIface graph, int vertexNr, int[] state) {
         state[vertexNr] = OPENED;
         for(Integer i : graph.getEdges(vertexNr)){
             if(state[i] == FRESH) doOrdering(graph, i, state);
             else if(state[i] == OPENED) throw new IllegalArgumentException("Graf obsahuje cykly");
         }
         System.out.print(" -> " + vertexNr);
         state[vertexNr] = CLOSED;
     }