class Solution(object): def lengthOfLongestSubstring(self, s): max_sub_length = 0 start = 0 s_length = len(s) for end in range(1, s_length): if s[end] in s[start:end]: start = s[start:end].index(s[end]) + 1 + start else: max_sub_length = max(max_sub_length, end - start + 1) return max_sub_length