算法面试题：最长回文子串
leetcode算法题目：
给定一个字符串 s，找到 s 中最长的回文子串。你可以假设 s 的最大长度为 1000
public static void main(String[] args) {
longestPalindrome("babad");
}
public static String longestPalindrome(String s) {
if (s.isEmpty()){
return "";
}
if (s.length() == 1) {
return s;
}
if(s.length() == 2){
String s1 = s.substring(0, 1);
String s2 = s.substring(1, 2);
if(s1.equals(s2)) {
return s;
}else{
return s1;
}
}
String ret = "";
StringBuffer stringBuffer = new StringBuffer ();
for (int i = 0; i < s.length()-1; i++) {
Character chi = s.charAt(i);
if(ret.isEmpty()) {
ret = chi.toString();
}
for(int j = s.length()-1; j > i;j--){
Character chj = s.charAt(j);
if(chi.equals(chj)){
//倒排
String tempS = s.substring(i, j+1);
stringBuffer.delete(0, stringBuffer.length());
stringBuffer.append(tempS);
String tempS2 = stringBuffer.reverse().toString();
if(tempS.equals(tempS2) && ret.length() < tempS.length()){
//是回响
ret = tempS;
break;
}
}
}
}
return ret;
}