代码1

Runtime: 23 ms, faster than 81.64% of Java online submissions for Longest Palindromic Substring.

class Solution {
    private int low, max;
    public String longestPalindrome(String s) {
        if (s.length() < 2) return s;
        for (int i = 0; i < s.length() - 1; i++) {
            extendPalindrome(s, i, i);
            extendPalindrome(s, i, i + 1);
        }
        return s.substring(low, low + max);
    }
    public void extendPalindrome(String s, int left, int right) {
        while (left >= 0 && right < s.length()) {
            if (s.charAt(left) == s.charAt(right)) {
                left--;
                right++;
            }else {
                break;
            }
        }
        if (max < right - left - 1) {
            max = right - left - 1;
            low = left + 1;
        }
    }
}