题解 | #删除字符串中出现次数最少的字符#

import java.util.Scanner;

import java.util.Map;
import java.util.HashMap;
import java.lang.Character;

// 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 a = in.nextLine();
            System.out.println(solution(a));
        }
    }

    public static String solution(String str) {

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

        for (int i = 0; i < str.length(); i++) {
            char cha = str.charAt(i);
            Integer count = countMap.get(cha);
            if (null == count) {
                countMap.put(cha, 1);
            } else {
                countMap.put(cha, count+1);
            }
        }
        Integer min = null;
        for (Integer val : countMap.values()) {
            if (null == min) {
                min = val;
            } else {
                min = val < min ? val : min;
            }
        }

        for (Character cha : countMap.keySet()) {
            if (countMap.get(cha).equals(min)) {
                str = str.replace(String.valueOf(cha), "");
            }
        }
        return str;
    }
}