【重点】【滑动窗口】3. 无重复字符的最长子串

题目
参考《算法小抄》重的解法，重点理解！！！

Python

参考：灵茶山艾府

Counter版

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        cntS = Counter()
        res, left = 0, 0
        for right, x in enumerate(s):
            cntS[x] += 1
            while cntS[x] > 1:
                cntS[s[left]] -= 1
                left += 1
            res = max(res, right - left + 1)
        
        return res

常见版

class Solution:
    def lengthOfLongestSubstr