Longest Palindromic Substring

1. Title

Longest Palindromic Substring

2. Http address

https://leetcode.com/problems/longest-palindromic-substring/

3. The question

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.

4. My code (AC)

    // Accepted
    public static String longestPalindrome(String s) {
         
        if ( s == null)
            return s;
        int len = s.length();
        if ( len <= 1)
            return s;
        boolean isPalindrome[][] = new boolean[len][len];
        int start = 0;
        int maxLen = 0;
        for(int i = 0 ; i < len; i++)
        {
            isPalindrome[i][i] = true;
            start = i;
            maxLen = 1;
        }
        
        for(int i = 0 ; i < len - 1; i++)
        {
            if ( s.charAt(i) == s.charAt(i+1)){
                isPalindrome[i][i+1] = true;
                start = i;
                maxLen = 2;
            }
        }
        
        for( int i = len - 3; i >=0 ; i--)
        {
            for( int j = i + 2; j < len; j++)
            {
                if( s.charAt(i) == s.charAt(j) && isPalindrome[i+1][j-1])
                {
                    isPalindrome[i][j] = true;
                    if ( maxLen < (j - i + 1))
                    {
                        start = i;
                        maxLen = j - i + 1;
                    }
                }
            }
        }
        for( int i = 0 ; i < len ; i++)
        {
            System.out.println();
            for( int j = 0 ; j < len ; j++)
            {
                System.out.print(" " + isPalindrome[i][j]);
            }
            System.out.println();
        }
        System.out.println(start);
        System.out.println(maxLen);
        return s.substring(start, start + maxLen);
    }