replace

import java.util.HashMap;

class Solution {
    public int characterReplacement(String s, int k) {
        HashMap<Character, Integer> freqMap = new HashMap<>();
        int maxFreq = 0;
        int maxLen = 0;
        int left = 0;

        for (int right = 0; right < s.length(); right++) {
            char c = s.charAt(right);
            freqMap.put(c, freqMap.getOrDefault(c, 0) + 1);

            maxFreq = Math.max(maxFreq, freqMap.get(c));

            // If replacements needed exceed k, shrink window
            while ((right - left + 1) - maxFreq > k) {
                char leftChar = s.charAt(left);
                freqMap.put(leftChar, freqMap.get(leftChar) - 1);
                left++;
            }

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

        return maxLen;
    }
}