def lengthOfLongestSubstring(self, s: str) -> int:
if len(s) == 0 : return 0
lookup = []
max_len = 0
cur_len = 0
for i in range(len(s)):
while s[i] in lookup:
lookup.pop(0)
lookup.append(s[i])
cur_len = len(lookup)
if cur_len > max_len:max_len = cur_len
return max_len
上述代码块的时间复杂度分析