leetcode 5. Longest Palindromic Substring

Compared with official solution, below code is easier to implement.
Because I don't think I can come up with

            start = i - (len - 1) / 2;
            end = i + len / 2;

in a interview.

class Solution {
    public String longestPalindrome(String s) {
        int len = 0, N = s.length();
        String ret = "";
        for (int i = 0; i < N; ++i) {
            int offset = maxL(s, i, i);
            if (2 * offset - 1 > len) {
                len = 2 * offset - 1;
                ret = s.substring(i - offset + 1, i + offset);
            }
            offset = maxL(s, i, i + 1);
            if (2 * offset > len) {
                len = 2 * offset;
                ret = s.substring(i - offset + 1, i + 1 + offset);
            }
        }
        return ret;
    }
    
    public int maxL(String s, int left, int right) {
        int i = 0, N = s.length();
        for (;left - i >= 0 && right + i < N && s.charAt(left - i) == s.charAt(right + i); ++i);
        return i;
    }
    
}