题解 | #密码截取#

import java.util.Scanner;

//建议参考HJ85最长回文字符串，一模一样

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        char[] str = in.nextLine().toCharArray();
        int max = 0;
        int[][] dp = new int[str.length + 1][str.length + 1];
        for (int i = 1; i <= str.length; i++) {
            dp[i][i] = 1;
        }
        for (int i = str.length - 1; i >= 1; i--) {
            for (int j = i + 1; j <= str.length; j++) {
                if (j - i == 1) {
                    if (str[i - 1] == str[j - 1]) {
                        dp[i][j] = 1;
                        max = Math.max(j - i + 1, max);
                    } else {
                        dp[i][j] = 0;
                    }
                } else {
                    if (str[i - 1] == str[j - 1] && dp[i + 1][j - 1] != 0) {
                        dp[i][j] = 1;
                        max = Math.max(j - i + 1, max);
                    } else {
                        dp[i][j] = 0;
                    }

                }
            }
        }
        System.out.println(max);
    }
}