5. Longest Palindromic Substring

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example:

Input: "babad"

Output: "bab"

Note: "aba" is also a valid answer.

 Example:

Input: "cbbd"

Output: "bb"
题目含义：查找最长的回文子串

class Solution {
   private int low, maxLen;

    private void huiwen(String s, int i, int j) {
        while (i >= 0 && j < s.length() && s.charAt(i) == s.charAt(j)) {
            i--;
            j++;
        }
        if (maxLen < j - i - 1) {
            low = i + 1;
            maxLen = j - i - 1;
        }
    }
    public String longestPalindrome(String s) {
        if (s.length() < 2) return s;
        for (int i = 0; i < s.length()-1; i++) {
            huiwen(s, i, i);
            huiwen(s, i, i + 1);
        }
        return s.substring(low, low+maxLen);  
    }
}