public static LenvstnDFA SubsetConstruct(LenvstnNFA nfa)
{
ResetState();
LenvstnDFA dfa = new LenvstnDFA();
// Sets of NFA states which is represented by some DFA state
Set <Set <state> > markedStates = new Set <Set <state> >();
Set <Set <state> > unmarkedStates = new Set <Set <state> >();
// Gives a number to each state in the DFA
Dictionary <Set <state>, state> dfaStateNum = new Dictionary <Set <state>, state>();
Set <state> nfaInitial = new Set <state>();
nfaInitial.Add(nfa.initial);
// Initially, EpsilonClosure(nfa.initial) is the only state in the DFAs states
// and it's unmarked.
Set <state> first = EpsilonClosure(nfa, nfaInitial);
unmarkedStates.Add(first);
// The initial dfa state
state dfaInitial = GenNewState();
dfaStateNum[first] = dfaInitial;
dfa.start = dfaInitial;
while (unmarkedStates.Count != 0)
{
// Takes out one unmarked state and posteriorly mark it.
Set <state> aState = unmarkedStates.Choose();
// Removes from the unmarked set.
unmarkedStates.Remove(aState);
// Inserts into the marked set.
markedStates.Add(aState);
// If this state contains the NFA's final state, add it to the DFA's set of
// final states.
if (aState.Where(state => nfa.final.Contains(state)).Count() > 0)
{
dfa.final.Add(dfaStateNum[aState]);
}
IEnumerator <input> iE = nfa.inputs.GetEnumerator();
// For each input symbol the NFA knows...
while (iE.MoveNext())
{
// Next state
Set <state> next = EpsilonClosure(nfa, nfa.Move(aState, iE.Current));
if (next.IsEmpty)
{
continue;
}
// If we haven't examined this state before, add it to the unmarkedStates,
// and make up a new number for it.
if (!unmarkedStates.Contains(next) && !markedStates.Contains(next))
{
unmarkedStates.Add(next);
dfaStateNum.Add(next, GenNewState());
}
if (iE.Current != (char)LenvstnNFA.Constants.Any && iE.Current != (char)LenvstnNFA.Constants.EpsilonAny)
{
KeyValuePair <state, input> transition = new KeyValuePair <state, input>(dfaStateNum[aState], iE.Current);
dfa.transTable[transition] = dfaStateNum[next];
}
else
{
if (!dfa.defaultTrans.ContainsKey(dfaStateNum[aState]))
{
dfa.defaultTrans.Add(dfaStateNum[aState], dfaStateNum[next]);
}
}
}
}
return(dfa);
}
