0 を偶数個含む文字列の言語を受理する DFA

dfa.py

"""
0 を偶数個含む文字列の言語を受理する DFA
"""
from enum import Enum, auto


class DFA:
    def __init__(self, states, alphabets, transition_method, start_state, accept_state):
        # self.states = states
        # self.alphabets = alphabets
        self.transition_method = transition_method
        # self.start_state = start_state
        self.accept_state = accept_state

        self.cur_state = start_state

    def run(self, input_str: str) -> bool:
        """ 入力文字列を読み出し、受理するかどうかを返す
        """
        for s in input_str:
            self.cur_state = self.transition(s)
        return self.cur_state in self.accept_state

    def transition(self, alphabet):
        """ 遷移 """
        return self.transition_method.get((self.cur_state, alphabet))


class States(Enum):
    q1 = auto()
    q2 = auto()


# 遷移関数 f(q, a)
# 状態が q のときに、a を読みだしたときの遷移先を表す
transition_method = {
    (States.q1, "0"): States.q2,
    (States.q1, "1"): States.q1,
    (States.q2, "0"): States.q1,
    (States.q2, "1"): States.q2,
}


dfa = DFA(
    states={States.q1, States.q2},
    alphabets={"0", "1"},
    transition_method=transition_method,
    start_state=States.q1,
    accept_state={States.q1},
)


print(dfa.run("0101"))   # True
print(dfa.run("01010"))  # False