字符串解码问题

/*一串字母根据A-1、B-2、...、Y-25、Z-26加密，将一串数字密文解密，按字母大小顺序输出*/
/*测试用例：输入12，输出AB、L*/

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

//感觉用一个全局变量的哈希表可能会更简单一些二
void DFS(vector<string> &alps, string numsSub, string alpsSub) {
    if (numsSub.empty()) {
        alps.push_back(alpsSub);
        return;
    }
    if (numsSub.size() == 1) {
        if (numsSub[0] >= '1' && numsSub[0] <= '9') {
            alpsSub += string(1, numsSub[0] - '1' + 'A');
            alps.push_back(alpsSub);
        }
        //如果最后剩的是0，把之前得到的结果抛弃
        return;
    }
    //把打头的一个字母单独来看
    if (numsSub[0] >= '1' && numsSub[0] <= '9') {
        string temp = alpsSub + string(1, numsSub[0] - '1' + 'A');
        DFS(alps, numsSub.substr(1), temp);
    }
    //把打头的两个字母合并起来看
    if (numsSub[0] == '1') {
        string temp = alpsSub + string(1, numsSub[1] - '0' + 'J');;
        DFS(alps, numsSub.substr(2), temp);
    }
    if (numsSub[0] == '2' && numsSub[1] <= '6' && numsSub[1] >= '0') {
        string temp = alpsSub + string(1, numsSub[1] - '0' + 'T');
        DFS(alps, numsSub.substr(2), temp);
    }
}

int main() {
    string nums;
    cin >> nums;
    vector<string> alps;
    string numsSub = nums;
    string alpsSub;
    DFS(alps, numsSub, alpsSub);
    sort(alps.begin(),alps.end());
    for(auto str:alps)
        cout << str << endl;
}