424. Longest Repeating Character Replacement

public class Solution {    public int characterReplacement(String s, int k) {        int start=0;        int end=0;        int maxlength=0;        int len=s.length();        int[] count=new int[26];        int maxcount=0;        for(end=0;end<len;end++)        {            maxcount=Math.max(maxcount,++count[s.charAt(end)-'A']);            while(end-start+1-maxcount>k){                --count[s.charAt(start)-'A'];                start++;            }            maxlength=Math.max(end-start+1,maxlength);        }        return maxlength;    }}