题解 | #最长回文子串#dp切记倒着遍历！

import java.util.Scanner;

// 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) {
        Scanner in = new Scanner(System.in);
  
        String s = in.nextLine();
        boolean dp[][] = new boolean[s.length()][s.length()];
        for(int i = 0;i<s.length();i++){
            dp[i][i] = true;
        }
        int ans = Integer.MIN_VALUE;
        for(int i = s.length() - 1; i >= 0;i--){
            for(int j = i+1; j < s.length();j++){
                if(s.charAt(i) == s.charAt(j)){
                    if(i+1==j){
                        dp[i][j] = true;
                    }else{
                        if(dp[i+1][j-1])
                            dp[i][j] = true;
                    }
                }
                if(dp[i][j])
                    if(j-i + 1> ans){
                        ans = j-i+1;
                }
            }
        }
        System.out.println(ans);
    }
}