编译原理实验nfa转换dfac++代码

以下是使用C++编写的NFA转换DFA代码示例：

#include <iostream>
#include <vector>
#include <set>
#include <map>

using namespace std;

// 定义NFA结构体
struct NFA {
    int start_state;  // 起始状态
    vector<int> accept_states;  // 接受状态
    map<pair<int, char>, vector<int>> transitions;  // 转换函数
};

// 定义DFA结构体
struct DFA {
    set<int> states;  // 状态集合
    int start_state;  // 起始状态
    set<int> accept_states;  // 接受状态集合
    map<pair<int, char>, int> transitions;  // 转换函数
};

// 获取NFA中从state状态出发通过symbol转换可以到达的所有状态
vector<int> get_next_states(NFA nfa, int state, char symbol) {
    vector<int> next_states;
    if (nfa.transitions.count(make_pair(state, symbol))) {
        next_states = nfa.transitions[make_pair(state, symbol)];
    }
    return next_states;
}

// 获取NFA中从state状态出发可以到达的所有状态
set<int> epsilon_closure(NFA nfa, int state) {
    set<int> closure;
    closure.insert(state);

    bool changed = true;
    while (changed) {
        changed = false;
        for (int s : closure) {
            vector<int> next_states = get_next_states(nfa, s, 'e');
            for (int next_state : next_states) {
                if (closure.count(next_state) == 0) {
                    closure.insert(next_state);
                    changed = true;
                }
            }
        }
    }

    return closure;
}

// 将NFA转换为DFA
DFA nfa_to_dfa(NFA nfa) {
    DFA dfa;

    // 计算NFA的epsilon闭包
    set<int> start_state = epsilon_closure(nfa, nfa.start_state);
    dfa.states.insert(1);
    dfa.start_state = 1;
    if (nfa.accept_states.count(nfa.start_state)) {
        dfa.accept_states.insert(1);
    }
    map<set<int>, int> dfa_state_map;
    dfa_state_map[start_state] = 1;

    int curr_dfa_state = 1;
    set<int> unmarked_dfa_states;
    unmarked_dfa_states.insert(1);
    while (!unmarked_dfa_states.empty()) {
        int dfa_state = *unmarked_dfa_states.begin();
        unmarked_dfa_states.erase(unmarked_dfa_states.begin());

        set<int> nfa_states = dfa_state_map.inverse[dfa_state];
        for (char symbol = 'a'; symbol <= 'z'; symbol++) {
            set<int> next_states;
            for (int nfa_state : nfa_states) {
                set<int> next_nfa_states = epsilon_closure(nfa, nfa_state);
                for (int next_nfa_state : next_nfa_states) {
                    vector<int> transitions = get_next_states(nfa, next_nfa_state, symbol);
                    for (int transition : transitions) {
                        next_states.insert(transition);
                    }
                }
            }
            if (!next_states.empty()) {
                int next_dfa_state;
                if (dfa_state_map.count(next_states)) {
                    next_dfa_state = dfa_state_map[next_states];
                } else {
                    curr_dfa_state++;
                    dfa.states.insert(curr_dfa_state);
                    next_dfa_state = curr_dfa_state;
                    dfa_state_map[next_states] = next_dfa_state;
                    if (nfa.accept_states.count(next_states)) {
                        dfa.accept_states.insert(next_dfa_state);
                    }
                    unmarked_dfa_states.insert(next_dfa_state);
                }
                dfa.transitions[make_pair(dfa_state, symbol)] = next_dfa_state;
            }
        }
    }

    return dfa;
}

int main() {
    // 定义NFA
    NFA nfa;
    nfa.start_state = 0;
    nfa.accept_states = {2};
    nfa.transitions[make_pair(0, 'a')] = {1};
    nfa.transitions[make_pair(1, 'b')] = {2};
    nfa.transitions[make_pair(0, 'e')] = {3};
    nfa.transitions[make_pair(3, 'a')] = {4};
    nfa.transitions[make_pair(4, 'b')] = {2};

    // 将NFA转换为DFA
    DFA dfa = nfa_to_dfa(nfa);

    // 输出DFA
    cout << "DFA states: ";
    for (int state : dfa.states) {
        cout << state << " ";
    }
    cout << endl;

    cout << "DFA start state: " << dfa.start_state << endl;

    cout << "DFA accept states: ";
    for (int state : dfa.accept_states) {
        cout << state << " ";
    }
    cout << endl;

    cout << "DFA transitions: " << endl;
    for (auto it : dfa.transitions) {
        cout << "  " << it.first.first << " --" << it.first.second << "--> " << it.second << endl;
    }

    return 0;
}

该代码使用了C++ STL库中的容器类型，如vector、set和map等，以便更方便地实现算法逻辑。在主函数中，我们先定义了一个NFA，然后调用nfa_to_dfa函数将其转换为DFA，并输出DFA的各项属性。