Leetcode之longest Palindromic Substring 求最长回文子串

//{java}
//O(n^2)
public class Solution {
    public String longestPalindrome(String s) {
        int max1=0,a1=0,max2=0,a2=-1;
        for(int a=0;a<s.length();a++)
        {
            int i=0;
            while(a-i>=0 && a+i<s.length())
            {
                if(s.charAt(a-i)==s.charAt(a+i))
                {
                    i++;
                }else
                {
                    break;
                }
            }
           if(i-1>max1)
           {
               max1=i-1;
               a1=a;
           }
        }
        
        for(int a=0;a<s.length()-1;a++)
        {
            if(s.charAt(a)==s.charAt(a+1))
            {
                int i=0;
                while(a-i>=0&&a+1+i<s.length())
                {
                    if(s.charAt(a-i)==s.charAt(a+i+1))
                    {
                        i++;
                    }else
                    {
                        break;
                    }
                }
                if(i-1>=max2)
                {
                    max2=i-1;
                    a2=a;
                }
            }
        }
        int n1=0,n2=0;
        n1=1+max1*2;
        if(a2!=-1)
            n2=2+max2*2;
        if(n1>n2)
            return s.substring(a1-max1,a1+max1+1);
        else
            return s.substring(a2-max2,a2+1+max2+1);
        
    }
}