159 Longest Substring with At Most Two Distinct Characters
159. Longest Substring with At Most Two Distinct Characters
题目： https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/
难度 : Hard
class Solution(object):
def lengthOfLongestSubstringTwoDistinct(self, s):
"""
:type s: str
:rtype: int
"""
maps = {}
begin, end, counter, length = 0, 0, 0, 0
while end < len(s):
maps[s[end]] = maps.get(s[end], 0) + 1
if maps[s[end]] == 1:
counter += 1
end += 1 # end 永远指向下一个待处理的字符
while counter > 2:
maps[s[begin]] -= 1
if maps[s[begin]] == 0:
counter -= 1
begin += 1
length = max(length, end - begin) # 因此这里是```end - begin```而不是```end - begin + 1```
return length
