题解 | #字符串合并处理#逻辑简单

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);

        String input = in.nextLine();
        String[] split = input.split(" ");
        char[] odd = new char[(split[0].length() + split[1].length()) / 2];
        char[] even = new char[(split[0].length() + split[1].length()) - odd.length];
        boolean isEven = true;
        int ei = 0, oi = 0;
        for (int i = 0; i < split[0].length(); i++) {
            if (isEven) {
                even[i / 2] = split[0].charAt(i);
                isEven = !isEven;
                ++ei;
            } else {
                odd[i / 2] = split[0].charAt(i);
                isEven = !isEven;
                ++oi;
            }
        }

        for (int i = 0; i < split[1].length(); i++) {
            if (isEven) {
                even[i / 2 + ei] = split[1].charAt(i);
                isEven = !isEven;
            } else {
                odd[i / 2 + oi] = split[1].charAt(i);
                isEven = !isEven;
            }
        }

        Arrays.sort(even);
        Arrays.sort(odd);
        ei = oi = 0;
        isEven = true;
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < input.length() - 1; i++) {
            if (isEven) {
                builder.append(convert(even[ei++]));
                isEven = !isEven;
            } else {
                builder.append(convert(odd[oi++]));
                isEven = !isEven;
            }
        }

        System.out.println(builder);

    }

    private static char convert(char c) {
        if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' &&
                c <= 'f')) {
            int i = Integer.parseInt(String.valueOf(c), 16);
            String bs = new StringBuilder(Integer.toBinaryString(i)).reverse().toString();
            if (bs.length() < 4) {
                bs = bs + "0000".substring(bs.length());
            }
            int i1 = Integer.parseInt(bs, 2);
            return Integer.toString(i1, 16).toUpperCase().charAt(0);
        }
        return c;
    }
}