200_longest-palindromic-substring

/*
@Copyright:LintCode
@Author:   Monster__li
@Problem:  http://www.lintcode.com/problem/longest-palindromic-substring
@Language: Java
@Datetime: 17-03-07 15:38
*/

public class Solution {
    /**
     * @param s input string
     * @return the longest palindromic substring
     */
    public String longestPalindrome(String s) {
     int s_length=s.length();
     int index_front=0,index_back=1,palindrome_length;//index_back=index_front+palindrome_length-1;
     int i,palindrome_length_max=1;
     int max_index_front=0,max_index_back=0;
  int palindromelength[][]=new int[s_length+2][s_length+2];
  for(index_front=0; index_front<s_length; ++index_front)
    palindromelength[index_front][1] = 1;
  for(palindrome_length=2;palindrome_length<=s_length;palindrome_length++)
  {
   for(index_front=0;index_front<s_length&&(index_back=index_front+palindrome_length-1)<s_length;++index_front)
   {
    if(s.charAt(index_front)==s.charAt(index_back)&&palindromelength[index_front+1][palindrome_length-2]==palindrome_length-2)
     palindromelength[index_front][palindrome_length]=palindromelength[index_front+1][palindrome_length-2]+2;
    else
     palindromelength[index_front][palindrome_length]=Math.max(palindromelength[index_front+1][palindrome_length], palindromelength[index_front+1][palindrome_length-1]);
    if(palindrome_length_max<palindromelength[index_front][palindrome_length])
    {
     palindrome_length_max=palindromelength[index_front][palindrome_length];
     max_index_front=index_front;
     max_index_back=index_back;
    }
   }
  }
  return s.substring(max_index_front, max_index_back+1);
    }
}