819. 最常见的单词

 

思路：
1、将整个段落中的字母转成小写；
2、用各标点符号分割段落；
3、遍历2返回的list，统计不在禁用表中且出现次数最多的单词并返回。

import re

class Solution(object):
    def mostCommonWord(self, paragraph, banned):
        """
        :type paragraph: str
        :type banned: List[str]
        :rtype: str
        """
        # 段落中的字母全部转成小写
        paragraph = paragraph.lower()
        # 用多种标点符号和空格分割段落
        listpara = re.split(r'[!?\'.;,\s]\s*', paragraph)
        # print(listpara)
        # 计数器
        num = 0
        # 返回值，即出现次数最多，同时不在禁用列表中的单词
        ans = ""
        for i, ch in enumerate(listpara):
            if ch not in banned and listpara.count(ch) > num:
                num = listpara.count(ch)
                ans = ch
        return ans


if __name__ == '__main__':
    solution = Solution()
    print(solution.mostCommonWord("Bob hit a ball, the hit BALL flew far after it was hit.", ["hit"]))
    print(solution.mostCommonWord("a, a, a, a, b,b,b,c, c", ["a"]))