文章--LeetCode算法--LongestPalindromicSubstring

目录

• LongestPalindromicSubstring
  • 问题描述
  • 实例
  • 实现代码

LongestPalindromicSubstring

问题描述

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

实例

• Example:
  Input: "babad"
  Output: "bab"
  Note: "aba" is also a valid answer.
• Example:
  Input: "cbbd"
  Output: "bb"

实现代码

 public 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);
                extendPalindrome(s, i, i + 1);
            }
            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;
            }
        }