题解 | #删除字符串中出现次数最少的字符#

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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String code = in.next();
            HashMap<Character,Integer> memo = mapGenerator(code);
            int min = minValueCounter(memo);
            System.out.println(filterStringByCount(memo,code,min));

        }
    }
    // 对所有的元素个数进行统计
    private static HashMap<Character, Integer> mapGenerator(String input) {
        HashMap<Character, Integer> memo = new HashMap<>();
        for (char character : input.toCharArray()) {
            memo.put(character, memo.getOrDefault(character, 0) + 1);
        }
        return memo;

    }
    // 寻找最小的出现次数
    private static int minValueCounter(Map<Character, Integer> record) {
        int min = Integer.MAX_VALUE;
        for (Map.Entry<Character, Integer> entry : record.entrySet()) {
            min =  Math.min(min, entry.getValue());
        }
        return min;
    }
    //返回筛选后的字符串
    private static String filterStringByCount(Map<Character, Integer>record,
            String input, int min) {
        StringBuilder res = new StringBuilder();
        for (char c : input.toCharArray()) {
            if (record.get(c) > min) {
                res.append(c);
            }
        }
        return res.toString();
    }
}