protected bool ArcReduce(BinaryConstraint <T> arc)
{
var x = arc.VariableA;
var y = arc.VariableB;
bool change = false;
for (var i = 0; i < x.Domain.Count; i++)
{
var valueX = x.Domain[i];
x.Current = valueX;
bool satisfactionFound = false;
foreach (var valueY in y.Domain)
{
y.Current = valueY;
if (arc.Check())
{
satisfactionFound = true;
break;
}
}
if (!satisfactionFound)
{
Console.WriteLine("Reduced xd");
x.Domain.Remove(valueX);
change = true;
}
y.Current = default;
}
x.Current = default;
return(change);
}
// Pseudokod xDxD
// https://en.wikipedia.org/wiki/AC-3_algorithm
protected bool Ac3()
{
//List<(IVariable<T>, IVariable<T>)> workList = new List<(IVariable<T>, IVariable<T>)>();
List <BinaryConstraint <T> > workList = new List <BinaryConstraint <T> >();
foreach (var constraint in Constraints)
{
var cast = constraint as BinaryConstraint <T>;
if (cast != null)
{
workList.Add(cast);
BinaryConstraint <T> reverseConstraint = new BinaryConstraint <T>()
{
Check = cast.Check,
VariableA = cast.VariableB,
VariableB = cast.VariableA
};
workList.Add(reverseConstraint);
}
}
while (workList.Count > 0)
{
var arc = workList[0];
workList.RemoveAt(0);
if (ArcReduce(arc))
{
if (arc.VariableA.Domain.Count == 0)
{
return(false);
}
else
{
Constraints.ForEach(c =>
{
var cast = c as BinaryConstraint <T>;
IVariable <T> other = null;
if (cast.VariableA == arc.VariableA)
{
other = cast.VariableB;
}
if (cast.VariableB == arc.VariableA)
{
other = cast.VariableA;
}
if (other != null && other != arc.VariableB)
{
workList.Add(cast);
BinaryConstraint <T> reverseConstraint = new BinaryConstraint <T>()
{
Check = cast.Check,
VariableA = cast.VariableB,
VariableB = cast.VariableA
};
workList.Add(reverseConstraint);
}
});
}
}
}
return(true);
}
