LeetCode--005--最长回文子串(java)

 1 class Solution {
 2     public String longestPalindrome(String s) {
 3         if(s == null || s.length() == 0){
 4             return s;
 5         }
 6         String res = "";
 7         boolean[][] dp = new boolean[s.length()][s.length()];
 8         int max = 0;
 9         for(int j = 0;j < s.length();j++){
10             for(int i = 0;i <= j;i++){
11                 dp[i][j] = s.charAt(i) == s.charAt(j) &&(j-i<=2 || dp[i+1][j-1]);
12                 if(dp[i][j]){
13                     if(j-i+1 > max){
14                         max = j-i+1;
15                         res = s.substring(i,j+1);
16                     }
17                 }
18             }
19         }
20     return res;
21     }
22 }