_424.java

package com.fishercoder.solutions;

public class _424 {

    public static class Solution1 {
        //credit: https://discuss.leetcode.com/topic/63494/java-12-lines-o-n-sliding-window-solution-with-explanation
        public int characterReplacement(String s, int k) {
            int len = s.length();
            int[] count = new int[26];
            int start = 0;
            int maxCount = 0;
            int maxLength = 0;
            for (int 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(maxLength, end - start + 1);
            }
            return maxLength;
        }
    }
}