经典算法找最长回文

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”

这里写代码片

Note: “aba” is also a valid answer.
Example:

Input: "cbbd"Output: "bb"

思路：从回文中的中间一个或者两个出发，向两边找。记录每一个回文长度，最后得到最长的那个的位置，和长度

 class Solution {private int lo, maxLen;public String longestPalindrome(String s) {    int len = s.length();    if (len < 2)        return s;    for (int i = 0; i < len-1; i++) {        extendPalindrome(s, i, i);  //assume odd length, try to extend Palindrome as possible        extendPalindrome(s, i, i+1); //assume even length.    }    return s.substring(lo, lo + maxLen);}private void extendPalindrome(String s, int j, int k) {    while (j >= 0 && k < s.length() && s.charAt(j) == s.charAt(k)) {        j--;        k++;    }    if (maxLen < k - j - 1) {        lo = j + 1;        maxLen = k - j - 1;    }}}