2021-02-06：假设字符串str长度为N，请问最长回文子串的长度是多少？

[福大大架构师每日一题]

2021-02-06：假设字符串str长度为N，请问最长回文子串的长度是多少？#福大大架构师每日一题#

[KeepSayingNo]

把核心算法贡献出来

private static String getLongestString(String input, int mid) {
        int len = input.length();
        StringBuilder stringBuilderLeft = new StringBuilder();
        StringBuilder stringBuilderRight = new StringBuilder();
        stringBuilderRight.append(input.charAt(mid));
        for (int i = mid, j = mid; i > 0 && j<len-1; i--, j++) {
            if (input.charAt(i - 1) != input.charAt(j + 1)) {
                return stringBuilderLeft.reverse().append(stringBuilderRight).toString();
            }

            stringBuilderLeft.append(input.charAt(i - 1));
            stringBuilderRight.append(input.charAt(j + 1));
        }

        return stringBuilderLeft.reverse().append(stringBuilderRight).toString();
    }