/**
* 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));
}
/// <summary>
/// Template method, which can be configured by overriding the three primitive operations below.
/// </summary>
/// <param name="csp"></param>
/// <param name="assignment"></param>
/// <returns>An assignment (possibly incomplete if task was cancelled) or null if no solution was found.</returns>
private Assignment <VAR, VAL> backtrack(CSP <VAR, VAL> csp, Assignment <VAR, VAL> assignment)
{
Assignment <VAR, VAL> result = null;
if (assignment.isComplete(csp.getVariables()) || currIsCancelled)
{
result = assignment;
}
else
{
VAR var = selectUnassignedVariable(csp, assignment);
foreach (VAL value in orderDomainValues(csp, assignment, var))
{
assignment.add(var, value);
fireStateChanged(csp, assignment, var);
if (assignment.isConsistent(csp.getConstraints(var)))
{
IInferenceLog <VAR, VAL> log = inference(csp, assignment, var);
if (!log.isEmpty())
{
fireStateChanged(csp, null, null);
}
if (!log.inconsistencyFound())
{
result = backtrack(csp, assignment);
if (result != null)
{
break;
}
}
log.undo(csp);
}
assignment.remove(var);
}
}
return(result);
}