题解 | #密码截取#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) { 
            String str = in.nextLine();
            int res = 0;
            for (int i = 0; i < str.length(); i++) {
                StringBuilder sti = new StringBuilder();
                StringBuilder stj = new StringBuilder();
                int m = 0;
                for (int j = str.length() - 1; j >= 0; j--) {
                    if ((i + m) >= str.length()) {
                        if (pan(sti.toString(), stj.toString()) && m > res) res = m;
                        break;
                    }
                    if (str.charAt(i + m) == str.charAt(j)) {
                        sti.append(str.charAt(i + m));
                        stj.append(str.charAt(j));
                        m++;
                        if (pan(sti.toString(), stj.toString()) && m > res) {
                            res = m;
                        }
                    } else {
                        if (pan(sti.toString(), stj.toString()) && m > res) res = m;
                        sti.setLength(0);
                        stj.setLength(0);
                        j = j + m;
                        m = 0;
                    }
                }
            }
            System.out.println(res);
        }
    }
    public static boolean pan(String b, String c) {
        for (int i = 0; i < b.length(); i++) {
            if (b.charAt(i) != c.charAt(c.length() - 1 - i)) {
                return false;
            }
        }
        return true;
    }
}