public class LongestPalindromicSubstring {    public String longestPalindrome(String s) {        StringBuilder sb = new StringBuilder(s);         int[] p = new int[2*s.length()+3]; //p数组用来保存每个字符的回文半径        sb.insert(0, ‘?‘); //这里在开头和结尾设置两个不同的字符，是为了向两边扫描的时候设置字符对比结束，sb最终结果为(?#...#!)        for(int i=0;i<=s.length();i++){            sb.insert(2*i+1, ‘#‘);        }        sb.insert(2*s.length()+2, ‘!‘);        int maxL=0,maxId=0,id=0;   //maxL是最长的半径        int i;        for(i=1;i<p.length-1;i++){            if(maxId > i){                p[i] = min(p[2*id-i], maxId-i);            }else{                p[i] = 1;            }            while(sb.charAt(i+p[i]) == sb.charAt(i-p[i])){                p[i]++;            }            /*if(p[i] + i > maxId){                maxId = p[i]+i;                id = i;            }*/            if(p[i] > maxL){                maxL = p[i];                id = i;                maxId = p[i]+i;            }        }        int index = 2*id - maxId + 1;        index = (index+1)/2-1;        return s.substring(index, p[id]-1+index);    }        private int min(int a, int b){        return a<b?a:b;    }    public static void main(String[] args) {        String s = "ababcbaba";        String palindrome = new LongestPalindromicSubstring().longestPalindrome(s);        System.out.println(palindrome);    }}