class Solution:
def lengthOfLongestSubstring(self, s: str) -> int:
mydict = collections.defaultdict(int)
l = 0
res = 0
for r, char in enumerate(s):
mydict[char] += 1
while mydict[char] > 1:
mydict[s[l]] -= 1
l += 1
res = max(res, r - l + 1)
return res
时间复杂度：O(n)
空间复杂度：O(1)
双指针/记录位置
class Solution:
def lengthOfLongestSubstring(self, s: str) -> int:
mydict = {}
start = 0
res = 0
for i, char in enumerate(s):
if char not in mydict:
dist = i - start + 1
res = max(res, dist)
else:
if mydict[char] >= start:
start = mydict[char] + 1
else:
res = max(res, i - start + 1)
mydict[char] = i
return res
class Solution(object):
def lengthOfLongestSubstring(self, s):
left = 0
res = 0
for right, char in enumerate(s):
pos = s.find(char, left, right) # 维护一个dict来储存pos而不是每次都使用find来找
if pos >= 0:
left = pos + 1
if right - left + 1 > res:
res = right - left + 1
return res