题解 | #删除字符串中出现次数最少的字符#

import java.util.*;
import java.util.stream.Collectors;
// 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 input = in.nextLine();
            Map<String, Integer> v = count(input);
            Integer min = v.values().stream().min((o1, o2) -> o1.compareTo(o2)).get();

            Set<String> repeated = v.entrySet().stream().filter(x->{
                return x.getValue().equals(min);
            }).map(x->{
                return x.getKey();
            }).collect(Collectors.toSet());


            char[] chars = input.toCharArray();
            StringBuilder sb = new StringBuilder();
            for(char c:chars){
                if(repeated.contains(String.valueOf(c))){
                    continue;
                }
                sb.append(String.valueOf(c));

            }
            System.out.println(sb.toString());
        }
    }

    public static Map<String, Integer> count(String val) {
        Map<String, Integer> m = new HashMap<>();
        char[] chars = val.toCharArray();
        for (char c : chars) {
            if (!m.containsKey(String.valueOf(c))) {
                m.put(String.valueOf(c), 1);
            } else {
                Integer v = m.get(String.valueOf(c)) + 1;
                m.put(String.valueOf(c), v);
            }
        }
        return m;

    }
}