Longest Palindromic Substring(最长回文子串)

Posted 2021-02-08 wkcode

Description:

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

Example 1:

Input: "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:

Input: "cbbd"
Output: "bb"

1，暴力法

　　判断字符串s的所有子串a是否为回文字符串，如果是，则返回字符串a与其长度l。最终返回长度最长的回文子串。

class Solution {
    public String longestPalindrome(String s) {
        String s1;
        String st = null;
        int maxLenrth = 0;
        if (s.length() == 1 || s.length() == 0) {
            return s;
        }else {
            for (int i = 0; i < s.length(); i++) {
                for (int j = i; j < s.length(); j++) {
                    s1 = s.substring(i, j+1);
                    if (isHw(s1)>maxLenrth) {
                        maxLenrth = isHw(s1);
                        st = s1;
                    }
                }
            }
            return st;
        }
    }
    
　　//判断是否为回文  是返回其长度  否返回0
    public int isHw(String s){
        
        for (int i = 0; i < s.length()/2; i++) {
            if (s.charAt(i) != s.charAt(s.length()-i-1)) {
                return 0;
            }
        }
        return s.length();
    }
}

 2，...