字母矩阵形式的NFA

下面是一个使用Python代码示例，将正则表达式转换为字母矩阵形式的NFA：

class NFA:
    def __init__(self, regex):
        self.states = set()
        self.alphabet = set()
        self.transitions = {}
        self.start_state = None
        self.accept_states = set()

        self.construct_nfa(regex)

    def construct_nfa(self, regex):
        stack = []
        for char in regex:
            if char == '(':
                stack.append(char)
            elif char == ')':
                while stack[-1] != '(':
                    self.process_operator(stack.pop())
                stack.pop()
            elif char in ['*', '|', '+']:
                while stack and stack[-1] != '(':
                    self.process_operator(stack.pop())
                stack.append(char)
            else:
                self.process_character(char)

        while stack:
            self.process_operator(stack.pop())

    def process_character(self, char):
        self.states.add(tuple([len(self.states)]))
        self.alphabet.add(char)
        if len(self.states) == 1:
            self.start_state = tuple(self.states)
        self.states.add(tuple([len(self.states)]))
        self.transitions[tuple([len(self.states) - 2]), char] = tuple([len(self.states) - 1])

    def process_operator(self, operator):
        if operator == '*':
            state = tuple([len(self.states)])
            self.states.add(state)
            self.transitions[state, ''] = self.start_state
            self.start_state = state
        elif operator == '|':
            state = tuple([len(self.states)])
            self.states.add(state)
            self.transitions[state, ''] = self.start_state

            state2 = tuple([len(self.states)])
            self.states.add(state2)
            self.transitions[tuple([len(self.states) - 2]), ''] = state2

            state3 = tuple([len(self.states)])
            self.states.add(state3)
            self.transitions[state3, ''] = self.start_state

            state4 = tuple([len(self.states)])
            self.states.add(state4)
            self.transitions[state3, ''] = tuple([len(self.states) - 1])

            self.start_state = state3
            self.accept_states.add(state4)
        elif operator == '+':
            state = tuple([len(self.states)])
            self.states.add(state)
            self.transitions[tuple([len(self.states) - 2]), ''] = state

            state2 = tuple([len(self.states)])
            self.states.add(state2)
            self.transitions[state2, ''] = self.start_state

            self.start_state = state2
            self.accept_states.add(state)

    def to_matrix(self):
        matrix = [['-' for _ in range(len(self.alphabet))] for _ in range(len(self.states))]

        for (state, char), next_state in self.transitions.items():
            state_index = list(self.states).index(state)
            char_index = list(self.alphabet).index(char)
            next_state_index = list(self.states).index(next_state)
            matrix[state_index][char_index] = next_state_index

        return matrix


# 示例用法
nfa = NFA('(a|b)*abb+')
matrix = nfa.to_matrix()
for row in matrix:
    print(row)

这个代码示例中的 NFA 类接受一个正则表达式作为参数，并将其转换为字母矩阵形式的NFA。 to_matrix 方法将转换后的NFA表示为一个二维矩阵，其中行表示状态，列表示输入字符，矩阵中的每个元素表示从一个状态通过输入字符到达的下一个状态。

示例中的正则表达式为 (a|b)*abb+，它表示以任意数量的 a 或 b 开头，后跟字符串 abb，最后至少有一个 b。输出结果是一个字母矩阵，表示NFA的状态转移。