题解 | #字符串合并处理#

import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String str = sc.nextLine();
            str = sort(str.replaceAll(" ",""));
            String[] arr = str.split("");
            StringBuilder sbr = new StringBuilder();
            int n =0;
            String strbin = null;
            StringBuilder sb = new StringBuilder();
            for(String s : arr){
                if(s.matches("[0-9]")){
                    //先转为数字
                     n = Integer.parseInt(s);
                    //转为二进制字符串
                     strbin = Integer.toBinaryString(n);
                    //转为StringBuilder
                     sb.append(strbin);
                    if(strbin.length() < 4){
                        for(int i = 4;i>strbin.length();i--){
                            sb.insert(0,"0");
                        }
                    }
                    int p = Integer.parseInt(sb.reverse().toString(),2);
                    sbr.append(Integer.toHexString(p).toUpperCase());
                }
                else if(s.matches("[a-fA-F]")){
                    //先转为数字
                    n = Integer.parseInt(s,16);
                    //转为二进制字符串
                    strbin = Integer.toBinaryString(n);
                    //转为StringBuilder
                    sb.append(strbin);
                    int p = Integer.parseInt(sb.reverse().toString(),2);
                    sbr.append(Integer.toHexString(p).toUpperCase());
                }else{
                    sbr.append(s);
                }
                sb.delete(0,sb.length());
            }
            System.out.println(sbr.toString());
            
        }
    }
    //奇偶分开排序
    private static String sort(String str){
        ArrayList<Character> Jlist = new ArrayList<Character>();
        ArrayList<Character> Olist = new ArrayList<Character>();
        char[] arr = str.toCharArray();
        for(int i=0;i<arr.length;i++){
            if(i%2==0){
                //偶数
                Jlist.add(arr[i]);
            }else{
                Olist.add(arr[i]);
            }
        }
        Jlist.sort((a,b) -> {return a-b;});
        Olist.sort((a,b) -> {return a-b;});
        StringBuilder sb = new StringBuilder();
        for(int i=0;i<Jlist.size();i++){
            sb.append(Jlist.get(i));
            if(i<Olist.size()){
                sb.append(Olist.get(i));
            }
            
        }
        return  sb.toString();
    }
}