• 欢迎光临~

# 424. Longest Repeating Character Replacement 改变k个字母，形成最长的连续

You are given a string `s` and an integer `k`. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most `k` times.

Return the length of the longest substring containing the same letter you can get after performing the above operations.

Example 1:

```Input: s = "ABAB", k = 2
Output: 4
Explanation: Replace the two 'A's with two 'B's or vice versa.
```

Example 2:

```Input: s = "AABABBA", k = 1
Output: 4
Explanation: Replace the one 'A' in the middle with 'B' and form "AABBBBA".
The substring "BBBB" has the longest repeating letters, which is 4.滑动窗口可以不限制多大，只限制左右aaababb:所以不能只看最长啊，计算长度的方法是int lettersToChange = (right - left + 1) - mostFreqLetter;参考：https://leetcode.com/problems/longest-repeating-character-replacement/discuss/358879/Java-Solution-Explained-and-Easy-to-Understand-for-Interviews```
```class Solution {
public int characterReplacement(String s, int k) {
int[] freq = new int[26];
int mostFreqLetter = 0;
int left = 0;
int max = 0;

for(int right = 0; right < s.length(); right++){
freq[s.charAt(right) - 'A']++;
mostFreqLetter = Math.max(mostFreqLetter, freq[s.charAt(right) - 'A']);

int lettersToChange = (right - left + 1) - mostFreqLetter;
if(lettersToChange > k){
freq[s.charAt(left) - 'A']--;
left++;
}

max = Math.max(max, right - left + 1);
}

return max;
}
}```

` `