class Solution {

public String longestPalindrome(String s) {

if(s == null || s.length() == 0) return null;

String result = "";

for(int i = 0; i < s.length(); i++) {

String s1 = lph(s, i, i);

if(s1.length() > result.length()) result = s1;

if(i < s.length()-1) {

s1 = lph(s, i, i+1);

if(s1.length() > result.length()) result = s1;

}

}

return result;

}

private String lph(String s, int l, int r) {

if(l > r) return "";

while(l >= 0 && r < s.length() && s.charAt(l) == s.charAt(r)){

l--;

r++;

}

return s.substring(l+1, r);

}

}