老铁，我第一题思路跟你基本一样，但为啥是0AC啊，给看一眼 package aiqiyi; import java.util.Arrays; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Scanner; import java.util.Set; public class _1 {     public static void main(String[] args) {         Scanner sc = new Scanner(System.in);         int res = 0;         String s = sc.nextLine();         int k = Integer.valueOf(sc.nextLine().split("")[0]);         Map<Character, Integer> map = new HashMap<>();         int length = s.length();         for (int i = 0; i < length; i++) {             if (map.containsKey(s.charAt(i))) {                 int m = map.get(s.charAt(i));                 map.put(s.charAt(i), m + 1);             } else                 map.put(s.charAt(i), 1);         }         Set<Map.Entry<Character, Integer>> set = map.entrySet();         int[] num = new int[map.size()];         Iterator it = set.iterator();         int i = 0;         while (it.hasNext()) {             Map.Entry m = (Map.Entry) it.next();             num[i] = (int) m.getValue();             i++;         }         System.out.println(map.toString());         Arrays.sort(num);         for (int m = 0; m < k; m++) {             num[map.size() - 1]--;             Arrays.sort(num);         }         for (int m = 0; m < map.size(); m++) {             res += (num[m] * num[m]);         }         System.out.println(res);     } }