LintCode:最长无重复字符的子串

class Solution:
# @param s: a string
# @return: an integer
def lengthOfLongestSubstring(self, s):
# write your code here
L = []
max_len = 0
n = 0
i = 0
while i < len(s):
for j in range(i, len(s)):
if s[j] not in L:
L.append(s[j])
n += 1
if n > max_len:
max_len = n
else:
tmp = L.index(s[j])
i += tmp
L = []
n = 0
break
i += 1
return max_len