题解 | #最长回文子串#

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

public class Main{
    public static void main(String [] args) throws Exception{
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        String str = bf.readLine();
        char [] arr = str.toCharArray();
        int count=0;
        for(int i = 1; i < arr.length; i++){
            if(arr[i] == arr[i-1]){
                int num = calc(arr, i-1,i);
                count = num >count ? num : count;
            }else if (i+1<arr.length &&arr[i+1] == arr[i-1]){
                int num = calc(arr, i-1,i+1)+1;
                count = num >count ? num : count;
            }
        }
        System.out.println(count);



    }

    public static int calc(char[] arr, int left,int right){
        int count=0;
        while(left>=0 && right<arr.length){
            if (arr[left--] != arr[right++]){
                break;
            }
            count+=2;
        }
        return count;
    }
}