NFA to DFA conversion

/*
 * Author : Kartik Kukreja
 * Description :    Program to convert a given NFA to the corresponding DFA.
            It reads in the NFA from "NFA.txt" and writes out the corresponding DFA to "DFA.txt".

            "NFA.txt" must have the following format:
                N M
                F a1 a2 ... af
                T
                s1 y1 T1 t1 t2 ... tt1
                s2 y2 T2 t1 t2 ... tt2
                 :
                 :
            Here,   N -> No. of states (states are numbered 0 ... N-1), 0 is the start state
                M -> Size of input alphabet (input symbols are
                    numbered 1 ... M and 0 is reserved for epsilon)
                F -> No. of final states, followed by F states ( 0 <= ai <= N-1)
                T -> No. of transitions, followed by T lines
                si -> Previous state ( 0 <= si <= N-1)
                yi -> Input symbol or epsilon ( 0 <= yi <= M)
                Ti -> No. of states the NFA moves from si on input yi, followed by Ti states

            "DFA.txt" will have the following format:
                N M
                F a1 a2 ... af
                s1 y1 t1
                s2 y2 y2
                :
                :
            Here,   N -> No. of states in the DFA (states are numbered 0 ... N-1), 0 is the start state
                M -> Size of input alphabet (input symbols are numbered 1 ... M)
                F -> No. of final states followed by F states ( 0 <= ai <= N-1)
                si -> Previous state
                yi -> Input symbol
                ti -> Next state
            Each line until the end of file contains one transition ( si yi ti )
 */


#include <cstdio>
#include <fstream>
#include <iostream>
#include <bitset>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <set>
#define MAX_NFA_STATES 10
#define MAX_ALPHABET_SIZE 10
using namespace std;

// Representation of an NFA state
class NFAstate {
    public:
        int transitions[MAX_ALPHABET_SIZE][MAX_NFA_STATES];
        NFAstate()  {
            for(int i=0; i<MAX_ALPHABET_SIZE; i++)
                for(int j=0; j<MAX_NFA_STATES; j++)
                    transitions[i][j] = -1;
        }
} *NFAstates;

// Representation of a DFA state
struct DFAstate {
    bool finalState;
    bitset<MAX_NFA_STATES> constituentNFAstates;
    bitset<MAX_NFA_STATES> transitions[MAX_ALPHABET_SIZE];
    int symbolicTransitions[MAX_ALPHABET_SIZE];
};

set <int> NFA_finalStates;
vector <int> DFA_finalStates;
vector <DFAstate*> DFAstates;
queue <int> incompleteDFAstates;
int N, M;   // N -> No. of stattes, M -> Size of input alphabet

// finds the epsilon closure of the NFA state "state" and stores it into "closure"
void epsilonClosure(int state, bitset<MAX_NFA_STATES> &closure )    {
    for(int i=0; i<N && NFAstates[state].transitions[0][i] != -1; i++)
        if(closure[NFAstates[state].transitions[0][i]] == 0)    {
            closure[NFAstates[state].transitions[0][i]] = 1;
            epsilonClosure(NFAstates[state].transitions[0][i], closure);
        }
}

// finds the epsilon closure of a set of NFA states "state" and stores it into "closure"
void epsilonClosure(bitset<MAX_NFA_STATES> state, bitset<MAX_NFA_STATES> &closure) {
    for(int i=0; i<N; i++)
        if(state[i] == 1)
            epsilonClosure(i, closure);
}

// returns a bitset representing the set of states the NFA could be in after moving
// from state X on input symbol A
void NFAmove(int X, int A, bitset<MAX_NFA_STATES> &Y)   {
    for(int i=0; i<N && NFAstates[X].transitions[A][i] != -1; i++)
        Y[NFAstates[X].transitions[A][i]] = 1;
}

// returns a bitset representing the set of states the NFA could be in after moving
// from the set of states X on input symbol A
void NFAmove(bitset<MAX_NFA_STATES> X, int A, bitset<MAX_NFA_STATES> &Y)   {
    for(int i=0; i<N; i++)
        if(X[i] == 1)
            NFAmove(i, A, Y);
}

int main()  {
    int i, j, X, Y, A, T, F, D;

    // read in the underlying NFA
    ifstream fin("NFA.txt");
    fin >> N >> M;
    NFAstates = new NFAstate[N];
    fin >> F;
    for(i=0; i<F; i++)    {
        fin >> X;
        NFA_finalStates.insert(X);
    }
    fin >> T;
    while(T--)   {
        fin >> X >> A >> Y;
        for(i=0; i<Y; i++)  {
            fin >> j;
            NFAstates[X].transitions[A][i] = j;
        }
    }
    fin.close();

    // construct the corresponding DFA
    D = 1;
    DFAstates.push_back(new DFAstate);
    DFAstates[0]->constituentNFAstates[0] = 1;
    epsilonClosure(0, DFAstates[0]->constituentNFAstates);
    for(j=0; j<N; j++)
        if(DFAstates[0]->constituentNFAstates[j] == 1 && NFA_finalStates.find(j) != NFA_finalStates.end())  {
            DFAstates[0]->finalState = true; DFA_finalStates.push_back(0); break;
        }
    incompleteDFAstates.push(0);
    while(!incompleteDFAstates.empty()) {
        X = incompleteDFAstates.front(); incompleteDFAstates.pop();
        for(i=1; i<=M; i++)  {
            NFAmove(DFAstates[X]->constituentNFAstates, i, DFAstates[X]->transitions[i]);
            epsilonClosure(DFAstates[X]->transitions[i], DFAstates[X]->transitions[i]);
            for(j=0; j<D; j++)
                if(DFAstates[X]->transitions[i] == DFAstates[j]->constituentNFAstates)  {
                   DFAstates[X]->symbolicTransitions[i] = j;    break;
                }
            if(j == D)   {
                DFAstates[X]->symbolicTransitions[i] = D;
                DFAstates.push_back(new DFAstate);
                DFAstates[D]->constituentNFAstates = DFAstates[X]->transitions[i];
                for(j=0; j<N; j++)
                    if(DFAstates[D]->constituentNFAstates[j] == 1 && NFA_finalStates.find(j) != NFA_finalStates.end())  {
                        DFAstates[D]->finalState = true; DFA_finalStates.push_back(D); break;
                    }
                incompleteDFAstates.push(D);
                D++;
            }
        }
    }

    // write out the corresponding DFA
    ofstream fout("DFA.txt");
    fout << D << " " << M << "\n" << DFA_finalStates.size();
    for(vector<int>::iterator it=DFA_finalStates.begin(); it!=DFA_finalStates.end(); it++)
        fout << " " << *it;
    fout << "\n";
    for(i=0; i<D; i++)  {
        for(j=1; j<=M; j++)
            fout << i << " " << j << " " << DFAstates[i]->symbolicTransitions[j] << "\n";
    }
    fout.close();

    return 0;
}