题解 | #最长回文子串#

import java.util.*;


// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String str  = in.nextLine();
            //尋找所有重疊的坐標
            List<int[]> coordinate = new ArrayList<>();
            for (int i = 0, k = 1 ; k < str.length(); k++, i++) {
                if (str.charAt(i) == str.charAt(k)) {
                    int a [] = {i, k};
                    coordinate.add(a);
                }
            }
            //雙重循環尋找最大值
            int max = 0;
            int result = 0;

            for (int[] cor : coordinate) {
                for (int x = cor[0], y = cor[1]; x >= 0 && y <= str.length() - 1; x--, y++) {
                    if (str.charAt(x) == str.charAt(y)) {
                        max = y - x + 1;
                    }else{
                        break;
                    }
                }
                result = Math.max(result, max);
                max = 0;
            }
            int singleton = 0;
            for (int i = 0; i < str.length(); i++) {
                for (int k = i - 1, z = i + 1; k >= 0 && z < str.length(); k--, z++) {
                    if (str.charAt(k) == str.charAt(z)) {
                        singleton = z - k + 1;
                    }
                    if (str.charAt(k) != str.charAt(z)) {
                        result = Math.max(result, singleton);
                        singleton = 0;
                        break;
                    }
                }

            }
            System.out.print(result);
        }

    }
}