LeetCode-5. Longest Palindromic Substring

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本文介绍了一种高效算法来找出给定字符串中的最长回文子串。通过判断中心扩展的方法，该算法能够处理最大长度为1000的字符串，并提供详细的实现步骤和示例。

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example:

Input: "babad"

Output: "bab"

Note: "aba" is also a valid answer.

Example:

Input: "cbbd"

Output: "bb"

class Solution {
    public String longestPalindrome(String s) {
		char[] ch = s.toCharArray();
		int left = 0, right = 0;
		int max = 0;
		for (int i = 0; i < ch.length; i++) {
			if (judge(ch, i-max-1, i)) {
				left=i-max-1; right = i;
				max += 2;
			}else if(judge(ch, i-max, i)) {
				left=i-max; right = i;
				max += 1;
			}
		}
		return s.substring(left, right+1);
	}

	public static boolean judge(char[] ch, int l, int r) {
		if (l < 0)
			return false;
		while (l < r) {
			if (ch[l++] != ch[r--])
				return false;
		}
		return true;
	}
}