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longest-palindromic-substring.java
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longest-palindromic-substring.java
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// 5. 最长回文子串 - Medium
// https://leetcode-cn.com/problems/longest-palindromic-substring/
package java;
class LongestPalindromicSubstring {
// 暴力解法
// 遍历出所有的子串,找出最长的回文串
public String longestPalindrome(String s) {
int len = s.length();
int maxLength = 1;
String longestPalindrome = "" + s.charAt(0);
for (int i = 0; i < len; i++) {
StringBuilder sb = new StringBuilder("" + s.charAt(i));
for (int j = i + 1; j < len; j++) {
sb.append(s.charAt(j));
if (isPalindrome(sb.toString())) {
if (sb.length() > maxLength) {
longestPalindrome = sb.toString();
maxLength = sb.length();
}
}
}
if (maxLength == len) break;
}
return longestPalindrome;
}
private boolean isPalindrome(String s) {
int len = s.length();
int left = 0, right = len - 1;
while (left <= right) {
if (s.charAt(left) != s.charAt(right)) {
return false;
}
left++;
right--;
}
return true;
}
}