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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
           String s = in.nextLine();
           //字符串转字符数组
           char[] charArr = s.toCharArray();
            Map<Character,Integer> charCountMap = new HashMap<Character,Integer>();
           for(char c:charArr){
                Integer count = charCountMap.get(c);
                if(count==null){
                    charCountMap.put(c,1);
                }else{
                    charCountMap.put(c,count+1);
                }
           }

            //查找出现次数最少得字符，也可能是多个字符
           List<Character> list = new ArrayList<Character>();
          
           Object[] countArrayObj =charCountMap.values().toArray();
           Integer[] countArrayInteger = new Integer[countArrayObj.length];
            for(int i=0;i<countArrayObj.length;i++){
                    countArrayInteger[i] = Integer.parseInt(countArrayObj[i].toString());
            }
           Arrays.sort(countArrayInteger);
           int count= countArrayInteger[0];
           for(Map.Entry<Character,Integer> entry:charCountMap.entrySet()){
            if(count == entry.getValue()){
                list.add(entry.getKey());
            }            
           }
            //删除出现次数最少得字符
           StringBuffer sb = new StringBuffer();
           for(char c:charArr){
            if(!list.contains(c)){
                sb.append(c);
            }
           }
            //输出删除后的字符
           System.out.println(sb.toString());       


           
        }
    }
}