滑动窗口 & 双指针

https://leetcode.cn/problems/longest-repeating-character-replacement/

class Solution {
public:
    int characterReplacement(string s, int k) {
        if(s.empty()){
            return 0;
        }
        vector<int> v(26);
        // 滑动窗口初始化，右边界每一步都在变化，直到边界
        int left = 0, right = 0, maxx = 0;
        for(right = 0; right < s.length(); right++){
            int temp = s[right] - 'A';
            v[temp]++;
            maxx = max(v[temp], maxx);
            if(right - left + 1 > maxx + k){
                v[s[left] - 'A']--;
                left++;
            }
        }
        // 返回滑动窗口的大小
        return s.length() - left;
    }
};