kleedy：只会python。。。 思路和一楼的一样 def lengthOfLongestSubstring(s):     used = {}     maxl = left = 0     for i in range(len(s)):         if s[i] in used and left <= used[s[i]]:             left = used[s[i]]+1         else:             maxl = max(maxl, i - left + 1)         used[s[i]] = i     return maxl