题解 | #密码截取#

import java.util.*; 
import java.io.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            String s = br.readLine();
            boolean[][] array = new boolean[s.length()][s.length()];
            for (int i = 0; i < s.length(); i++) {
                array[i][i] = true;
            }
            int res = Integer.MIN_VALUE;
            for (int r = 1; r < s.length(); r++) {
                for (int l = 0; l < r; l++) {
                    if (s.charAt(l) == s.charAt(r) && (r - l <= 2 || array[l + 1][r - 1] == true)) {
                        array[l][r] = true;
                        res = Math.max(res, r - l + 1);
                    }
                }
            }
            System.out.println(res);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}