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public class Solution424 {
    public static int characterReplacement(String s, int k) {
        int i = 0, j = 0, max_len = 0, current_char = s.charAt(0);
        int n = s.length();
        if (n == 0) {
            return 0;
        }
        int k_remaining = k;
        while (j < n) {
            if (s.charAt(j) == current_char) {
                j++;
            } else {
                if (k_remaining > 0) {
                    current_char = s.charAt(j) = current_char;
                    k_remaining--;
                } else {
                    int window_length = j - i + 1;
                    if (window_length > max_len) {
                        max_len = window_length;
                    }
                    i = j + 1;
                    if (i < n) {
                        current_char = s.charAt(i);
                    }
                }
            }
        }
        return max_len;
    }
    public static void main(String[] args) {
        // ????1
        String s = "ABAB";
        int k = 2;
        System.out.println(characterReplacement(s, k)); // ??4
        // ????2
        String s = "AABABBA";
        int k = 1;
        System.out.println(characterReplacement(s, k)); // ??4
        // ????3
        String s = "ABBB";
        int k = 2;
        System.out.println(characterReplacement(s, k)); // ??4
    }
}

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