424. Longest Repeating Character Replacement

class Solution:
    def characterReplacement(self, s: str, k: int) -> int:
        l = 0

        chaSet = {}

        res = 0

        for r in range(len(s)):
            chaSet[s[r]] = chaSet.get(s[r], 0) + 1

            while (r - l + 1) - max(chaSet.values()) > k:
                chaSet[s[l]] -= 1
                l += 1
            res = max(res, r - l + 1)

        return res