public static IEnumerable <string> Search(string oriWord, int maxDist, TrieDictionary dict)
{
LenvstnNFA nfa = LenvstnNFA.BuildNFA(oriWord, maxDist);
//nfa.Show();
LenvstnDFA dfa = SubsetMachine.SubsetConstruct(nfa);
//dfa.Show();
List <string> output = new List <string>();
DFSserach(dfa, dfa.start, dict.Root, output);
return(output);
}
/// <summary>
/// Builds the Epsilon closure of states for the given NFA
/// </summary>
/// <param name="nfa"></param>
/// <param name="states"></param>
/// <returns></returns>
static Set <state> EpsilonClosure(LenvstnNFA nfa, Set <state> states)
{
if (states.IsEmpty)
{
return(states);
}
// Push all states onto a stack
Stack <state> uncheckedStack = new Stack <state>(states);
// Initialize EpsilonClosure(states) to states
Set <state> epsilonClosure = states;
while (uncheckedStack.Count != 0)
{
// Pop state t, the top element, off the stack
state t = uncheckedStack.Pop();
int i = 0;
// For each state u with an edge from t to u labeled Epsilon
foreach (input input in nfa.transTable[t])
{
if (input == (char)LenvstnNFA.Constants.EpsilonAny)
{
state u = Array.IndexOf(nfa.transTable[t], input, i);
// If u is not already in epsilonClosure, add it and push it onto stack
if (!epsilonClosure.Contains(u))
{
epsilonClosure.Add(u);
uncheckedStack.Push(u);
}
}
i = i + 1;
}
}
return(epsilonClosure);
}
/// <summary>
/// NFA building functions, build a NFA to find all words within given levenshtein distance from given word.
/// </summary>
/// <param name="str">The input word</param>
/// <param name="maxDist">The max levenshtein distance from input word</param>
/// <returns></returns>
public static LenvstnNFA BuildNFA(String str, int maxDist)
{
int width = str.Length + 1;
int height = maxDist + 1;
int size = width * height;
Set <state> final = new Set <state>();
for (int i = 1; i <= height; ++i)
{
final.Add(i * width - 1);
}
LenvstnNFA nfa = new LenvstnNFA(size, 0, final);
//Every state except those in right most coulmn in the matrix
for (int e = 0; e < height; ++e)
{
for (int i = 0; i < width - 1; ++i)
{
//trans to right
nfa.AddTrans(e * width + i, e * width + i + 1, str[i]);
if (e < (height - 1))
{
//trans to upper
nfa.AddTrans(e * width + i, (e + 1) * width + i, (char)Constants.Any);
//trans to diagonal upper
nfa.AddTrans(e * width + i, (e + 1) * width + i + 1, (char)Constants.EpsilonAny);
}
}
}
//right most column
for (int k = 1; k < height; ++k)
{
//trans to upper
nfa.AddTrans(k * width - 1, (k + 1) * width - 1, (char)Constants.Any);
}
return(nfa);
}
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);
}