Shortest Palindrome leetcode-java

先制作原字符串的对称镜像字符串，如s = “abcd”, 镜像a = “abcddcba”+” “。
然后对新字符串a，按KMP算法求next的方法，求next
KMP算法请参考：
http://blog.csdn.net/tukangzheng/article/details/38438481

public class Solution {      public String shortestPalindrome(String s) {          if(s.length() == 0||s.length() == 1)              return s;              String mirror = s + new StringBuilder(s).reverse().toString()+" ";         int[] next = new int[mirror.length()];        int i=0;        int j=-1;        next[0]=-1;        while(i<mirror.length()-1){            if(j==-1||mirror.charAt(i)==mirror.charAt(j)){                i++;                j++;                next[i]=j;            }else j=next[j];        }        int count = s.length() - next[mirror.length() -1];          if(count<0)count =0;        String result = new StringBuilder(s.substring(s.length()-count, s.length())).reverse().toString() + s;          return result;      }  }