字符串中选择最长无重复字串问题

def lengthOfLongestSubstring(self, s):
from collections import defaultdict
length,i,d=0,0,defaultdict(int)
for j in range(len(s)):
if d[s[j]]>i:
length=max(length,j-i)
i=d[s[j]]
d[s[j]]=j+1;
length=max(length,len(s)-i)
return length

def lengthOfLongestSubstring(self, s):
d,start,length={},0,0
for i,j in enumerate(s):
if j in d:
length=max(length,i-start)
start=max(start,d[j]+1) # 小心
d[j]=i
return max(length,len(s)-start)