菜鸟的每日力扣系列——2047. 句子中的有效单词数

import re
def re_solution(sentence: str) -> int:
    return sum(bool(re.match("^[a-z]*([a-z]-[a-z])?[a-z]*[.!,]?$", word)) for word in sentence.split() if word)

def countValidWords(sentence: str) -> int:
    def helper(word) -> bool:
        flag = False
        n = len(word)
        for i, c in enumerate(word):
            if c.isdigit() or (c in "!.," and i < n -1):
                return False
            if c == '-':
                if flag or i == 0 or i == n - 1 or not word[i-1].islower() or not word[i+1].islower():
                    return False
                flag = True
        return True
    return sum(helper(word) for word in sentence.split() if word)