DFA* nfa_to_dfa(NFA *& nfa) {
	DFA *dfa = new DFA();
	cout <<"nfa size:" << nfa->get_states().size() << endl;
	//initial set.
	set<State*> inital_closure = nfa->get_start_state()->get_epsilon_closure();
	bool acceptance = false;
	int pattern_id = -1;
	for (State *s : inital_closure) {
		acceptance |= s->get_acceptance();
		pattern_id = get_new_pattern(pattern_id, s->get_pattern_id());
	}

	//Start state of DFA.
	State *inital_state = dfa->add_new_start_state(pattern_id, acceptance);

	//stack containing all unmakred states.
	stack <set<State*> > states_stack;
	states_stack.push(inital_closure);

	//map every subset NFA states to equvalent DFA state.
	map<set<State*>, State*> dfa_mapping;
	dfa_mapping[inital_closure] = inital_state;
	while (!states_stack.empty()) {
		set<State*> curr_states = states_stack.top();
		states_stack.pop();
		State *curr_dfa_state = dfa_mapping[curr_states];
		/*
		cout << "Curr State: ";
		for (State *s : curr_states)
			cout << s->get_state_id() << " ";
		cout << endl;
		*/
		for (unsigned char c = MIN_CHAR; c <= MAX_CHAR; c++) {
			set<State*> new_states = move(curr_states, c);
			//set<State*> new_states = epsilon_closure(temp);
			if (new_states.empty())
				continue;
			/*
			cout << "Curr transition: " << c << endl;;
			for (State *s : new_states)
				cout << s->get_state_id() << " ";
			cout << endl;
			*/
			if (!dfa_mapping.count(new_states)) {
				bool acceptance_state = false;
				int pattern_id = -1;
				for (State *s : new_states) {
					acceptance_state |= s->get_acceptance();
					pattern_id = get_new_pattern(pattern_id, s->get_pattern_id());
				}
				State * new_state = dfa->add_new_end_state(pattern_id, acceptance_state);
				dfa_mapping[new_states] = new_state;
				states_stack.push(new_states);
			}
			curr_dfa_state->add_transition(c, dfa_mapping[new_states]);
		}
	//	cout <<"States: "<< states_stack.size() << endl;
	}
	return dfa;
}