题解 | #密码截取#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc  = new Scanner(System.in);
        String in = sc.nextLine();
        String[] str = in.split("");
        System.out.println(longestPwd(str));
    }
    public static int longestPwd(String[] str) {
        int maxLong = 1;
        int n = str.length;
        int[] nums = new int[n];
        nums[0] = 1;
        for (int i = 1; i < n - 1; i++) {
		  //跳过相同的字符
            if (str[i].equals(str[i - 1])) {
                nums[i] = nums[i - 1];
                continue;
            }
            nums[i] = 1;
            int left = i - 1;
            int right = i + 1;
		  //找到左边第一个不同的字符
            while (left > 0 && str[left].equals(str[i])) {
                left--;
                nums[i]++;
            }
		  //找到右边第一个不同的字符
            while (right < n && str[right].equals(str[i])) {
                right++;
                nums[i]++;
            }
            for (int j = 0; right + j < n && left - j >= 0; j++) {
                if (str[left - j].equals(str[right + j])) {
                    nums[i] += 2;
                } else {
                    break;
                }
            }
        }
        for (int i = 0; i < n; i++) {
            maxLong = Math.max(maxLong, nums[i]);
        }
        return maxLong;
    }
}