求最大回文子串

基于java求最大回文子串

/**
 * @desc 求最长回文字符串
 * 采用中心扩展的方法来实现
 * https://blog.youkuaiyun.com/a1111116/article/details/115176747
 **/
public class MaxPalindrome {

    public String longestPalindrome(String s) {
        if (s.length() < 2) return s;
        char[] chars = s.toCharArray();
        int begin = 0;
        int maxLength = 0;
        for (int left=0; left < s.length() - 1; left ++) {
            int oddLen = expandAroundCenter(chars, left, left);
            int evenLen = expandAroundCenter(chars, left, left + 1);

            int curMaxLen = Math.max(oddLen, evenLen);
            if (curMaxLen > maxLength) {
                maxLength = curMaxLen;
                begin = left - (curMaxLen - 1) /2;
            }

        }
        return s.substring(begin, begin + maxLength);


    }

    private int expandAroundCenter(char[] chars, int left, int right) {
        while (left >= 0 && right < chars.length && chars[left] == chars[right]) {
            left --;
            right ++;
        }
        return right - left - 1;
    }
}