题解 | #字符串合并处理#

直接穷举，只有16个进行转换

import java.util.*;
public class Main{
    public static void main(String [] args){
        getString();
    }
    public static void getString(){
        Scanner scan = new Scanner(System.in);
        while(scan.hasNext()){
            String input = scan.nextLine().replace(" ", "");
            int len = input.length();
            int len1 = input.length()/2;
            int len2 = input.length()/2;
            if(len%2!=0){
                len1 += 1;
            }
            String [] str1 = new String[len1];
            String [] str2 = new String[len2];
            // 分别对奇数行偶数行排序
            for(int i = 0; i < len; i++){
                if(i % 2 == 0){
                    str1[i/2] = input.substring(i, i+1);
                }else{
                    str2[(i-1)/2] = input.substring(i, i+1);
                }
            }
            Arrays.sort(str1);
            Arrays.sort(str2);

            for(int i = 0; i < len1; i++){
                System.out.print(getChar(str1[i]));
                if(i < len2){
                    System.out.print(getChar(str2[i]));
                }
            }
            System.out.println("");
        }
    }

    // 16进制转换
    public static String getChar(String input){
        String temp = input.toUpperCase();
        switch(temp){
            case "F" :return "F";
            case "E" :return "7";
            case "D" :return "B";
            case "C" :return "3";
            case "B" :return "D";
            case "A" :return "5";
            case "9" :return "9";
            case "8" :return "1";
            case "7" :return "E";
            case "6" :return "6";
            case "5" :return "A";
            case "4" :return "2";
            case "3" :return "C";
            case "2" :return "4";
            case "1" :return "8";
            case "0" :return "0";
            default:return input;
        }
        /*
        1111 == 1111  F = F
        1110 == 0111  E = 7
        1101 == 1011  D = B
        1100 == 0011  C = 3
        1011 == 1101  B = D
        1010 == 0101  A = 5
        1001 == 1001  9 = 9
        1000 == 0001  8 = 1
        0111 == 1110  7 = E
        0110 == 0110  6 = 6
        0101 == 1010  5 = A
        0100 == 0010  4 = 2
        0011 == 1100  3 = C
        0010 == 0100  2 = 4
        0001 == 1000  1 = 8
        0000 == 0000  0 = 0*/
    }
}