只要注意点最长非重复字串出现在字符串末尾的情况就好，挺简单的。（时间和内存都惨不忍睹）

 

 

 

 

class Solution:    def lengthOfLongestSubstring(self, s: str) -> int:        string = s        #---        #lenth = 1        if string == "":            return 0        if len(string) == 1:            return 1        # # ---        # find substring        longestSubstring = 0        for start in range(len(string)):            for end in range(start +1 , len(string)):                if string[end] not in string[start:end]:  # find whether current letter duplication                    #---                    #check if there have letter after end                    #careful with the letter string[end]                    if end +1 == len(string):                        if (end - start +1) > longestSubstring:                            return (end - start +1)                        else:                            return longestSubstring                else:                    if len(string[start:end])  > longestSubstring:                        longestSubstring = len(string[start:end])                    break        return longestSubstring