用java实现查找字符串的最长子回文串

可以使用 Manacher 算法来实现查找字符串的最长子回文串，以下是 Java 代码示例：

public class LongestPalindromicSubstring {
public String longestPalindrome(String s) {
if (s == null || s.length() == 0) {
return "";
}
String t = preProcess(s);
int n = t.length();
int[] p = new int[n];
int center = 0, right = 0;
for (int i = 1; i < n - 1; i++) {
int mirror = 2 * center - i;
if (right > i) {
p[i] = Math.min(right - i, p[mirror]);
} else {
p[i] = 0;
}
while (t.charAt(i + 1 + p[i]) == t.charAt(i - 1 - p[i])) {
p[i]++;
}
if (i + p[i] > right) {
center = i;
right = i + p[i];
}
}
int maxLength = 0, centerIndex = 0;
for (int i = 1; i < n - 1; i++) {
if (p[i] > maxLength) {
maxLength = p[i];
centerIndex = i;
}
}
int start = (centerIndex - maxLength) / 2;
return s.substring(start, start + maxLength);
}

private String preProcess(String s) {
int n = s.length();
if (n == 0) {
return "^$";
}
StringBuilder sb = new StringBuilder("^");
for (int i = 0; i < n; i++) {
sb.append("#").append(s.charAt(i));
}
sb.append("#$");
return sb.toString();
}
}

注意：以上代码仅供参考，可能存在错误或不足之处，建议在实际使用时进行测试和优化。