字母卡片

想复杂了

用不到 hashmap排序

数组排序就可以了

学到了 hashmap 按值 排序方法

import java.util.Scanner;
import java.util.*;


public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(sc.hasNext()){
            int n = sc.nextInt();
            int k = sc.nextInt();
            sc.nextLine();

            String words = sc.nextLine();
            int [] freq = new int [26];
            HashMap<Character, Integer> t = new HashMap<Character, Integer> ();

            for(char c: words.toCharArray()) {
                if(t.containsKey(c)) t.put(c,t.get(c)+1);
                else t.put(c,1);

                int index = c-'A';
                freq[index]++;
            }
            //chushihua wanbi

            ArrayList<Map.Entry<Character, Integer>> l = new ArrayList(t.entrySet());
            Collections.sort(l, new Comparator<Map.Entry<?, Integer>>(){
                public int compare(Map.Entry<?, Integer> o2, Map.Entry<?, Integer> o1) {
                    return o1.getValue().compareTo(o2.getValue());
                }});

            long sum = 0;
            for (int i=0; i<l.size();i++){
                if(l.get(i).getValue()<=k) {
                    k = k-l.get(i).getValue();
                    sum = sum + (long) l.get(i).getValue() *l.get(i).getValue();
                }
                else{
                    sum = sum + (long) k *k;
                    k=0;
                }
            }
            System.out.println(sum);

        }

    }
}