/*
* 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;
}