Given a string s, return the longest

palindromic

substring

in

s

.

Example 1:

Input: s = "babad"
Output: "bab"
Explanation: "aba" is also a valid answer.

Example 2:

Input: s = "cbbd"
Output: "bb"

Constraints:

• 1 <= s.length <= 1000
• s consist of only digits and English letters.

中心拓展

class Solution {
    public String longestPalindrome(String s) {
        String res = "";
        int len = 0;
        for(int i = 0; i < s.length();i++){
           
            String left = subString(s, i, i);
            if(left.length() > len){
                res = left;
                len = left.length();
            }
            String rigth = subString(s, i, i + 1);
            if(rigth.length() > len){
                res = rigth;
                 len = rigth.length();
            }
        }
        return res;
    }
    String subString(String s, int start, int end){
        while(start >= 0 && end < s.length()){
            if(s.charAt(start) != s.charAt(end)){
                break;
            }
            start--;
            end ++;
        }
        return s.substring(start + 1, end);
    }
}

class Solution {
    public String longestPalindrome(String s) {
        String res = "";
        int len = 0;
        for(int i = 0; i < s.length();i++){
           
            String left = subString(s, i, i);
            if(left.length() > len){
                res = left;
                len = left.length();
            }
            String rigth = subString(s, i, i + 1);
            if(rigth.length() > len){
                res = rigth;
                 len = rigth.length();
            }
        }
        return res;
    }
    String subString(String s, int start, int end){
        while(start >= 0 && end < s.length()){
            if(s.charAt(start) != s.charAt(end)){
                break;
            }
            start--;
            end ++;
        }
        return s.substring(start + 1, end);
    }
}

class Solution {
    public String longestPalindrome(String s) {
        String res = "";
        int len = 0;
        for(int i = 0; i < s.length();i++){
           
            String left = subString(s, i, i);
            if(left.length() > len){
                res = left;
                len = left.length();
            }
            String rigth = subString(s, i, i + 1);
            if(rigth.length() > len){
                res = rigth;
                 len = rigth.length();
            }
        }
        return res;
    }
    String subString(String s, int start, int end){
        while(start >= 0 && end < s.length()){
            if(s.charAt(start) != s.charAt(end)){
                break;
            }
            start--;
            end ++;
        }
        return s.substring(start + 1, end);
    }
}