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LongestPalindromicSubstring.java
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LongestPalindromicSubstring.java
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package com.hncboy;
/**
* @author hncboy
* @date 2019/8/31 10:15
* @description 5.最长回文子串
*
* 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。
*
* 示例 1:
* 输入: "babad"
* 输出: "bab"
* 注意: "aba" 也是一个有效答案。
*
* 示例 2:
* 输入: "cbbd"
* 输出: "bb"
*/
public class LongestPalindromicSubstring {
public static void main(String[] args) {
System.out.println(longestPalindrome("cbbd"));
}
private static String longestPalindrome(String s) {
// 在第 103 个用例出错 input: "" output: ""
if (s.length() == 0) {
return "";
}
int min = 0;
int max = 1;
int left;
int right;
for (int i = 0; i < s.length(); i++) {
for (int j = 1; j < 3; j++) {
// j = 1 偶数回文 j = 2 奇数回文
left = i;
right = left + j;
while (left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
left--;
right++;
}
left++; // left >= 0
if (max - min < right - left) {
max = right;
min = left;
}
}
}
// 截取 [min, max)
return s.substring(min, max);
}
}