28实现strSTR（）

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        # 判断needle是否为NOne或者为空字符串
        if not needle or len(needle) == 0:
            return 0
        # 定义两个变量，用来接收needle的长度
        length,index = len(needle),0
        # 进行循环，当index的值
        while index <= len(haystack) - length:
            # 判断是否可以匹配
            if haystack[index : index + length] == needle:
                return index
            # 索引加一
            else:
                index += 1
        # 代表匹配失败，返回-1
        return -1

A = Solution()
print(A.strStr("hello","ll"))
print(A.strStr("helll","hahah"))