题解 | #HJ32 密码截取# (动归 *)

import java.io.InputStreamReader;
import java.util.Scanner;
import java.io.BufferedReader;
// 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) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String s = "";
        while ((s = br.readLine()) != null) {
            System.out.println(check(s));
        }
    }
    public static int check(String s) {
        int len = s.length(), ans = 0;
        boolean[][] dp = new boolean[len][len];
        for (int i = 0; i < len; i++) dp[i][i] = true;
        for (int r = 1; r < len; r++) {
            for (int l = 0; l < r; l++) {
                if (s.charAt(l) == s.charAt(r) && (r - l <= 2 || dp[l + 1][r - 1])) {
                    dp[l][r]=true;
                    ans=Math.max(ans,r-l+1);
                }
            }
        }
        return ans;
    }
}