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。
博客分享了作者在编译原理课程中使用C++实现NFA_DFA转化的过程，包括状态压缩、bfs和dfs算法。作者强调了图像输出的困难，介绍了如何用C#处理输出的txt文件来绘制图形，并提到使用向量法处理箭头绘制。代码已上传至优快云。
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