public override Assignment <VAR, VAL> solve(CSP <VAR, VAL> csp)
{
Assignment <VAR, VAL> assignment = new Assignment <VAR, VAL>();
// Select a root from the List of Variables
VAR root = _useRandom ? Util.selectRandomlyFromList(csp.getVariables()) : csp.getVariables().Get(0);
// Sort the variables in topological order
ICollection <VAR> orderedVars = CollectionFactory.CreateQueue <VAR>();
IMap <VAR, IConstraint <VAR, VAL> > parentConstraints = CollectionFactory.CreateInsertionOrderedMap <VAR, IConstraint <VAR, VAL> >();
topologicalSort(csp, root, orderedVars, parentConstraints);
if (csp.getDomain(root).isEmpty())
{
return(null); // CSP has no solution! (needed if orderedVars.size() == 1)
}
// Establish arc consistency from top to bottom (starting at the bottom).
csp = csp.copyDomains(); // do not change the original CSP!
for (int i = orderedVars.Size() - 1; i > 0; i--)
{
VAR var = orderedVars.Get(i);
IConstraint <VAR, VAL> constraint = parentConstraints.Get(var);
VAR parent = csp.getNeighbor(var, constraint);
if (makeArcConsistent(parent, var, constraint, csp))
{
fireStateChanged(csp, null, parent);
if (csp.getDomain(parent).isEmpty())
{
return(null); // CSP has no solution!
}
}
}
// Assign values to variables from top to bottom.
for (int i = 0; i < orderedVars.Size(); ++i)
{
VAR var = orderedVars.Get(i);
foreach (VAL value in csp.getDomain(var))
{
assignment.add(var, value);
if (assignment.isConsistent(csp.getConstraints(var)))
{
fireStateChanged(csp, assignment, var);
break;
}
}
}
return(assignment);
}
/**
* Applies an initial inference step and then calls the super class implementation.
*/
public override Assignment <VAR, VAL> solve(CSP <VAR, VAL> csp)
{
if (inferenceStrategy != null)
{
csp = csp.copyDomains(); // do not change the original CSP!
IInferenceLog <VAR, VAL> log = inferenceStrategy.apply(csp);
if (!log.isEmpty())
{
fireStateChanged(csp, null, null);
if (log.inconsistencyFound())
{
return(null);
}
}
}
return(base.solve(csp));
}