Leetcode 424. Longest Repeating Character Replacement

Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repeating letters you can get after performing the above operations.

这道题的思路是：遍历一遍字符串， 用max来记录字幕出现最多的次数。与此同时， 要保证子字符串的长度 (i  - start ) 减去 max 要小于等于 k（可以用于替换字母的个数）。

如果大于k时， 就需要移动window （start++）。

public class Solution {    public int characterReplacement(String s, int k) {        int start = 0, max = 0, len = s.length();        int[] arr = new int[26];        for (int i = 0; i < len; i++) {            max = Math.max(max, ++arr[s.charAt(i) - 'A']);            while (i - start - max >= k) {                arr[s.charAt(start) - 'A']--;                start++;            }        }        return len - start;    }}