晨哥Leetcode 424. Longest Repeating Character Replacement

Given a string s that consists of only uppercase English letters, you can perform at most k operations on that string.
In one operation, you can choose any character of the string and change it to any other uppercase English character.
Find the length of the longest sub-string containing all repeating letters you can get after performing the above operations.
Note:
Both the string’s length and k will not exceed 104.
Example 1:
Input:
s = “ABAB”, k = 2
Output:
4
Explanation:
Replace the two 'A’s with two 'B’s or vice versa.

解析：
比较容易想到是滑动窗口来做，但是需要知道重复次数最多的那个字符出现的次数
滑动窗口问题，maxCount直接：
maxCount = Math.max(maxCount, ++count[s.charAt(end) - ‘A’]);
maxCount代表的是曾经出现在这个窗口里的，最多的重复字符数量

public int characterReplacement(String s, int k) {
        int len = s.length();
        int[] count = new int[26]; //全是大写、小写字母，就用数组来存就好
        int start = 0, maxCount = 0, maxLength = 0;
        for (int end = 0; end < len; end++) {
            maxCount = Math.max(maxCount, ++count[s.charAt(end) - 'A']);//**曾经出现在这个窗口里的**，最多的重复字符数量
            while (end - start + 1 - maxCount > k) {
                count[s.charAt(start) - 'A']--;
                start++;
            }
            maxLength = Math.max(maxLength, end - start + 1);
        }
        return maxLength;
    }