第二题： import java.util.HashMap; import java.util.Scanner; import java.util.Map.Entry; public class Main {     public static void main(String[] args) {         Scanner scan = new Scanner(System.in);         int m = Integer.parseInt(scan.nextLine());         int n = Integer.parseInt(scan.nextLine());         HashMap<String, Integer> map = new HashMap<>();         int max = 0;         for (int i = 0; i < n; i++) {             String[] strs = scan.nextLine().split(" ");             int k = Integer.parseInt(strs[0]);             if (k > 0) {                 String[] zus = new String[k];                 for (int j = 0; j < k; j++) {                     StringBuilder sb = new StringBuilder();                     sb.append(strs[2 * j + 1]);                     sb.append(strs[2 * j + 2]);                     zus[j] = sb.toString();                 }                 if (map.size() == 0) {                     for (int j = 0; j < zus.length; j++) {                         map.put(zus[j], 1);                     }                 } else {                     HashMap<String, Integer> map2 = new HashMap<>();                     for (Entry<String, Integer> entry : map.entrySet()) {                         int nums = entry.getValue();                         for (int j = 0; j < zus.length; j++) {                             if (entry.getKey().equals(zus[j])) {                                 nums++;                                 if (nums > max)                                     max = nums;                                 map2.put(entry.getKey(), nums);                                 break;                             }                         }                     }                     map = new HashMap<>(map2);                 }             } else {                 map = new HashMap<>();             }         }         if (max <= 1)             System.out.println(1);         else             System.out.println(max);     } }