题解 | #删除字符串中出现次数最少的字符#

import java.util.Scanner;
import java.util.HashMap;

// 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);
        String s = in.nextLine();
        int min = 20;
        String move = "";
        String result = s;
        HashMap<String, Integer> hashMap = new HashMap<>();
        for (int i = 0; i < s.length(); i++) {
            if (hashMap.containsKey(String.valueOf(s.charAt(i))))
                hashMap.replace(String.valueOf(s.charAt(i)),
                                hashMap.get(String.valueOf(s.charAt(i))) + 1);
            else
                hashMap.put(String.valueOf(s.charAt(i)), 1);
        }
        for (int i = 0; i < s.length(); i++) {
            Integer num = hashMap.get(String.valueOf(s.charAt(i)));
            if (num < min) {
                min = num;
                move = "";
                move = move.concat(String.valueOf(s.charAt(i)));
            } else if (num == min) {
                move = move.concat(String.valueOf(s.charAt(i)));
            }
        }
        for (int i = 0; i < move.length(); i++)
            result = result.replace(String.valueOf(move.charAt(i)), "");
        System.out.println(result);
    }
}