n^2的方法
package String;
/**
* @Title: Longest_Palindromic_Substring.java
* @Package String
* @Description: TODO
* @author nutc
* @date 2013-8-27 下午8:31:39
* @version V1.0
*/
public class Longest_Palindromic_Substring {
public static void main(String args[]) {
Longest_Palindromic_Substring l = new Longest_Palindromic_Substring();
String s = "abb";
System.out.println(l.longestPalindrome(s));
}
public String longestPalindrome(String s) {
if (s == null || s.length() <= 1)
return s; // String 的长度有括号!
int longest = 0;
int index = 0;
char[] c = s.toCharArray();
for (int i = 1; i < c.length; i++) {
int now = getLong(c, i - 1, i + 1) + 1;
if (c[i] == c[i - 1])
now = Math.max(now, getLong(c, i - 2, i + 1)+2);
if (now > longest) {
longest = now;
index = i - now / 2;
}
}
return s.substring(index,index+ longest); // substring 小写啊 白痴,是index+ longest而不是longest !!!!
}
public int getLong(char[] s, int i, int j) {
int count = 0;
while (i >= 0 && j < s.length && s[i] == s[j]) {
i--;
j++;
count++;
}
return count * 2;
}
}