/**
* g must form a circuit
*
* @param g a directed graph variable
* @return a circuit constraint
*/
public static Constraint circuit(IDirectedGraphVar g) {
if (g.getMandatoryNodes().getSize() == g.getNbMaxNodes()) {
return hamiltonian_circuit(g);
}
return new Constraint(
"circuit",
new PropNodeDegree_AtLeast_Incr(g, Orientation.SUCCESSORS, 1),
new PropNodeDegree_AtLeast_Incr(g, Orientation.PREDECESSORS, 1),
new PropNodeDegree_AtMost_Incr(g, Orientation.SUCCESSORS, 1),
new PropNodeDegree_AtMost_Incr(g, Orientation.PREDECESSORS, 1),
new PropNbSCC(g, g.getSolver().ONE),
new PropCircuit(g));
}
/**
* Creates a constraint which states that d is the diameter of g i.e. d is the length (number of
* arcs) of the largest shortest path among any pair of nodes This constraint implies that g is
* strongly connected
*
* @param g a directed graph variable
* @param d an integer variable
* @return a constraint which states that d is the diameter of g
*/
public static Constraint diameter(IDirectedGraphVar g, IntVar d) {
return new Constraint("NbCliques", new PropNbSCC(g, g.getSolver().ONE), new PropDiameter(g, d));
}
/**
* Creates a strong connectedness constraint which ensures that g is strongly connected
*
* @param g a directed graph variable
* @return A strong connectedness constraint which ensures that g is strongly connected
*/
public static Constraint strongly_connected(IDirectedGraphVar g) {
return nb_strongly_connected_components(
g, VF.bounded("nbSCC", 0, g.getNbMaxNodes(), g.getSolver()));
}