lexical-analyzer/SubsetConstructor.cpp at main · ardafincan/lexical-analyzer · GitHub

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#include "SubsetConstructor.h"
using namespace std;

set<State *> SubsetConstructor::epsilonClosure(set<State *> states)
{
    set<State *> result = states;
    queue<State *> q;

    for (State *s : states)
    {
        q.push(s);
    }

    while (!q.empty())
    {
        State *current = q.front();
        q.pop();

        map<char, vector<State *>> transitions = current->getTransitions();
        if (transitions.find('\0') != transitions.end())
        {
            for (State *next : transitions['\0'])
            {
                if (result.find(next) == result.end())
                {
                    result.insert(next);
                    q.push(next);
                }
            }
        }
    }
    return result;
}

DFA *SubsetConstructor::constructDFA(NFA *nfa)
{
    DFA *dfa = new DFA();
    set<State *> startSet = epsilonClosure({nfa->getStartState()});
    CombinedState *startCS = new CombinedState(startSet);
    dfa->addState(startCS);
    dfa->setStartState(startCS);

    map<set<State *>, CombinedState *> visited;
    visited[startSet] = startCS;

    queue<set<State *>> q;
    q.push(startSet);

    while (!q.empty())
    {
        set<State *> curSet = q.front();
        q.pop();
        CombinedState *currentDfa = visited[curSet];
        CombinedState *nextDFA;

        for (char c : this->getAlphabet(nfa))
        {
            set<State *> nextSet;
            for (State *state : curSet)
            {
                map<char, vector<State *>> trans = state->getTransitions();
                if (state->getTransitions().find(c) != trans.end())
                {
                    for (State *target : trans[c])
                    {
                        nextSet.insert(target);
                    }
                }
            }
            nextSet = epsilonClosure(nextSet);

            if (nextSet.empty())
            {
                continue;
            }

            if (visited.find(nextSet) == visited.end())
            {
                nextDFA = new CombinedState(nextSet);
                visited[nextSet] = nextDFA;
                dfa->addState(nextDFA);
                q.push(nextSet);
            }
            else
            {
                nextDFA = visited[nextSet];
            }

            dfa->addTransition(currentDfa, c, nextDFA);
        }
    }

    for (auto &pair : visited)
    {
        set<State *> stateSet = pair.first;
        for (State *state : stateSet)
        {
            if (state->getAcceptance())
            {
                pair.second->isAccepting = true;
                break;
            }
        }
    }

    return dfa;
}

set<char> SubsetConstructor::getAlphabet(NFA *nfa)
{
    set<char> alphabet;
    map<char, vector<State *>> trans;

    for (State *state : nfa->getAllStates())
    {
        for (auto &pair : state->getTransitions())
        {
            char character = pair.first;
            if (character != '\0')
            {
                alphabet.insert(character);
            }
        }
    }
    return alphabet;
}