public static Automaton Intersection(Automaton a1, Automaton a2)
{
if (a1.IsSingleton)
{
return(a2.Run(a1.Singleton) ? a1.CloneIfRequired() : BasicAutomata.MakeEmpty());
}
if (a2.IsSingleton)
{
return(a1.Run(a2.Singleton) ? a2.CloneIfRequired() : BasicAutomata.MakeEmpty());
}
if (a1 == a2)
{
return(a1.CloneIfRequired());
}
var transitions1 = Automaton.GetSortedTransitions(a1.GetStates());
var transitions2 = Automaton.GetSortedTransitions(a2.GetStates());
var c = new Automaton();
var worklist = new LinkedList <StatePair>();
var newstates = new Dictionary <StatePair, StatePair>();
var p = new StatePair(c.Initial, a1.Initial, a2.Initial);
_ = worklist.AddLast(p);
newstates.Add(p, p);
while (worklist.Count > 0)
{
p = worklist.RemoveAndReturnFirst();
p.S.Accept = p.FirstState.Accept && p.SecondState.Accept;
var t1 = transitions1[p.FirstState.Number];
var t2 = transitions2[p.SecondState.Number];
for (int n1 = 0, b2 = 0; n1 < t1.Length; n1++)
{
while (b2 < t2.Length && t2[b2].Max < t1[n1].Min)
{
b2++;
}
for (var n2 = b2; n2 < t2.Length && t1[n1].Max >= t2[n2].Min; n2++)
{
if (t2[n2].Max >= t1[n1].Min)
{
var q = new StatePair(t1[n1].To, t2[n2].To);
_ = newstates.TryGetValue(q, out var r);
if (r == null)
{
q.S = new State();
_ = worklist.AddLast(q);
newstates.Add(q, q);
r = q;
}
var min = t1[n1].Min > t2[n2].Min ? t1[n1].Min : t2[n2].Min;
var max = t1[n1].Max < t2[n2].Max ? t1[n1].Max : t2[n2].Max;
p.S.Transitions.Add(new Transition(min, max, r.S));
}
}
}
}
c.IsDeterministic = a1.IsDeterministic && a2.IsDeterministic;
c.RemoveDeadTransitions();
c.CheckMinimizeAlways();
return(c);
}
