5. Longest Palindromic Substring，longestpalindromic

5. Longest Palindromic Substring，longestpalindromic

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

代碼如下：（逾時）

 1 public class Solution { 2     public String longestPalindrome(String s) { 3         if(s.length()==1||s.length()==0) 4         return s; 5         6         String t=" ",sub=" "; 7         int count=0,max=0; 8             char[] ss=s.toCharArray(); 9             for(int i=0;i<ss.length;i++)10             {11                 if(ss.length-i+1<=max)12                 return t;13                 for(int j=ss.length-1;j>i;j--)14                 {15                 if(ss[i]==ss[j]){16                     sub=s.substring(i,j+1);17                     count=j-i+1;18                     if(isPalindrome(sub)&&count>max)19                     {20                         t=sub;21                         max=count;22                         break;23                     }24                     }25                 }26             }27         return t;28         29     }30     public boolean isPalindrome(String a){31         char[] aa=a.toCharArray();32         int i=0,j=aa.length-1;33         while(i<=j)34         {35             if(aa[i]==aa[j])36             {i++;j--;}37             else return false;38         }39         return true;40     }41 }