题解 | #字符串合并处理#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String str1 = scanner.next();
            String str2 = scanner.next();
            String result = control1(str1, str2);
            result = control2(result);
            result = control3(result);
            System.out.println(result);
        }
    }



    private static String control1(String str1, String str2) {
        return str1+str2;
    }
    private static String control2(String result) {
        List<Character> list1 = new ArrayList<>();
        List<Character> list2 = new ArrayList<>();
        for (int i = 0; i < result.length(); i++) {
            if (i % 2 == 0) {
                list1.add(result.charAt(i));
            } else {
                list2.add(result.charAt(i));
            }
        }
        Collections.sort(list1);
        Collections.sort(list2);
        StringBuffer sb = new StringBuffer();
        while (true) {
            if (!list1.isEmpty()) {
                sb.append(list1.get(0));
                list1.remove(0);
            }
            if (!list2.isEmpty()) {
                sb.append(list2.get(0));
                list2.remove(0);
            }
            if (list1.isEmpty() && list2.isEmpty()) {
                break;
            }
        }
        return sb.toString();
    }
    private static String control3(String result) {
        StringBuffer result2 = new StringBuffer();
        for (int i = 0; i < result.length(); i++) {
            char oldChar = result.charAt(i);
            char c = Character.toLowerCase(oldChar);
            if (c >= '0' && c <= '9' || c >= 'a' && c <= 'f') {
                StringBuffer sb = new StringBuffer();
                sb.append(map.get(c));
                sb.reverse();
                char c2 = map2.get(sb.toString());
                if (c2 >= 'a' && c2 <= 'f') {
                    c2 = (char) (c2 - ('a' - 'A'));
                }
                result2.append(c2);
            } else {
                result2.append(oldChar);
            }
        }
        return result2.toString();
    }
    public static Map<Character, String> map = new HashMap<>();
    public static Map<String, Character> map2 = new HashMap<>();

    static{
        map.put('0',"0000");
        map.put('1',"0001");
        map.put('2',"0010");
        map.put('3',"0011");
        map.put('4',"0100");
        map.put('5',"0101");
        map.put('6',"0110");
        map.put('7',"0111");
        map.put('8',"1000");
        map.put('9',"1001");
        map.put('a',"1010");
        map.put('b',"1011");
        map.put('c',"1100");
        map.put('d',"1101");
        map.put('e',"1110");
        map.put('f',"1111");
        map.forEach((k,v)->{
            map2.put(v, k);
        });
    }

}