题解 | 删除字符串中出现次数最少的字符

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

// 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 str = in.nextLine();
        Map<Character, Integer> map = new HashMap<>();
        char[] charArray = str.toCharArray();
        for (int i = 0; i < charArray.length; i++) {
            map.put(charArray[i], map.getOrDefault(charArray[i], 0) + 1);
        }
        Set<String> set = new HashSet<>();
        int min = Integer.MAX_VALUE;

        for (Map.Entry<Character, Integer> entry : map.entrySet()) {
            if (entry.getValue() < min) {
                min = entry.getValue();
                set.clear();
                set.add(entry.getKey().toString());
            } else if (entry.getValue() == min) {
                set.add(entry.getKey().toString());
            }
        }
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < charArray.length; i++) {
            if (!set.contains(String.valueOf(charArray[i]))) {
                sb.append(charArray[i]);
            }
        }
        System.out.println(sb);
    }
}