class DigitTokenizer:
    def __init__(self):
        self.digit_char = "0123456789*%="
        self.special_tokens = ["<bos>", "<pad>", "<eos>", "<unk>"]
        self.vocab_list = list(self.digit_char) + self.special_tokens
        
        self.char_to_int = {char: i for i, char in enumerate(self.vocab_list)}
        self.int_to_char = {i: char for i, char in enumerate(self.vocab_list)}
        self.vocab_size = len(self.vocab_list)

    def encode(self, input_string: str) -> list[int]:
        return [self.char_to_int.get(char, self.char_to_int["<unk>"]) for char in input_string]

    def decode(self, token_ids: list[int]) -> str:
        decoded_chars = []
        for token_id in token_ids:
            char = self.int_to_char.get(token_id)
            if char == "<eos>":
                break
            if char is not None and char not in ["<pad>", "<unk>"]:
                decoded_chars.append(char)
                
        return "".join(decoded_chars)