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package jrummikub.ai.fdsolver.constraint;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import jrummikub.ai.fdsolver.Constraint;
import jrummikub.ai.fdsolver.Propagator;
import jrummikub.ai.fdsolver.Satisfiability;
import jrummikub.ai.fdsolver.Var;
public class SameConstraint<T> extends Constraint {
private Var<T> x, y;
Propagator propX, propY;
public SameConstraint(Var<T> x, Var<T> y) {
this.x = x;
this.y = y;
propX = new SameProp<T>(x, y);
propY = new SameProp<T>(y, x);
}
@Override
public Collection<Var<?>> getWatchedVars() {
return Arrays.<Var<?>> asList(x, y);
}
private class SameProp<T> implements Propagator {
private Var<T> x, y;
public SameProp(Var<T> x, Var<T> y) {
this.x = x;
this.y = y;
}
@Override
public Collection<Var<?>> getWatchedVars() {
return Arrays.<Var<?>>asList(y);
}
@Override
public void propagate() {
for(Iterator<T> i = x.iterator(); i.hasNext();) {
if(!y.getRange().contains(i.next())) {
i.remove();
}
}
}
}
@Override
public Collection<Propagator> getPropagators(boolean negate) {
return Arrays.asList(propX, propY);
}
@Override
public Satisfiability getSatisfiability() {
if (Collections.disjoint(x.getRange(), y.getRange())) {
return Satisfiability.UNSAT;
} else if (x.getRange().size() == 1 && y.getRange().size() == 1) {
return Satisfiability.TAUT;
} else {
return Satisfiability.SAT;
}
}
}
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