340. 至多包含 K 个不同字符的最长子串

滑动窗口

class Solution:
    def lengthOfLongestSubstringKDistinct(self, s: str, k: int) -> int:
        wds = collections.defaultdict(int)
        l, r = 0, 0
        res = 0
        while r < len(s):
            wds[s[r]] += 1
            r += 1
            
            while len(wds) > k:
                wds[s[l]] -= 1
                if wds[s[l]] == 0:
                    del wds[s[l]]
                l += 1

            res = max(res, r-l)

        return res