题解 | 删除字符串中出现次数最少的字符

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeMap;

// 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
        Map<Character, Integer> map = new HashMap<>();

        while (in.hasNext()) { // 注意 while 处理多个 case
            String a = in.nextLine();
            if (a == null || a.length() < 1) {
                continue;
            }
            int  n = a.length();
            int min = n;
            for (int i = 0; i < n; i++) {
                if (map.containsKey(a.charAt(i))) {
                    map.put(a.charAt(i), map.get(a.charAt(i)) + 1);
                } else {
                    map.put(a.charAt(i), 1);
                }
            }

            Set<Map.Entry<Character, Integer>> set = map.entrySet();
            for (Map.Entry<Character, Integer> c : set) {
                if (min >= c.getValue()) {
                    min = c.getValue();
                }
            }
            List<Character> charList = new ArrayList<>();
            for (Map.Entry<Character, Integer> c : set) {
                if (c.getValue() == min) {
                    charList.add(c.getKey());
                }
            }

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < n; i++) {
                if (!charList.contains(a.charAt(i))) {
                    sb.append(a.charAt(i));
                }
            }
            System.out.println(sb.toString());
        }
    }


}