【字符串】字符串合并处理

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
string code_book   = "0123456789ABCDEFabcdef";
string decode_book = "084C2A6E195D3B7F5D3B7F";
string code(string input) {
    string output;
    output = input;
    for (int i = 0; i < input.size(); i++)
    {
        for (int j = 0; j < code_book.size(); j++)
        {
            if (output[i]==code_book[j])
            {
                output[i] = decode_book[j];
                //*****************************************
                //必须写break，否则会被重复处理
                //*****************************************
                break;
            }
        }
    }
    return output;
}
int main() {
    string str_1;
    string str_2;
    while (cin>>str_1)
    {
        cin >> str_2;
        string str_all = str_1 + str_2;
        str_1.clear();
        str_2.clear();
        for (int i = 0; i < str_all.size(); i++)
        {
            if (i%2==0)
            {
                str_1+=str_all[i];
            }
            else
            {
                str_2 += str_all[i];
            }
        }
        sort(str_1.begin(), str_1.end());
        sort(str_2.begin(), str_2.end());
        int str_1_index = 0;
        int str_2_index = 0;
        for (int i = 0; i < str_all.size(); i++)
        {
            if (i % 2 == 0)
            {
                str_all[i] = str_1[str_1_index];
                str_1_index++;
            }
            else
            {
                str_all[i] = str_2[str_2_index];
                str_2_index++;
            }
        }
        str_all = code(str_all);
        cout << str_all << endl;
    }
}