LeetCode——Longest Palindromic Substring（最长回文子字符串）

代码：

class Solution {
    public String longestPalindrome(String s) {
        if (s == null || s.length() < 1) return "";
    int start = 0, end = 0;
    for (int i = 0; i < s.length(); i++) {
        int len1 = expandAroundCenter(s, i, i);
        int len2 = expandAroundCenter(s, i, i + 1);
        int len = Math.max(len1, len2);
        if (len > end - start) {
            start = i - (len - 1) / 2;
            end = i + len / 2;
        }
    }
    return s.substring(start, end + 1);
    }

private int expandAroundCenter(String s, int left, int right) {
    int L = left, R = right;
    while (L >= 0 && R < s.length() && s.charAt(L) == s.charAt(R)) {
        L--;
        R++;
    }
    return R - L - 1;
}
}

public class LongestPalindrome {
	public static void main(String[] args) {
		Solution s=new Solution();
		System.out.println(s.longestPalindrome("baab"));
	}
}

结果：

baab