01. Merge Trains

#include <iostream>
#include <string>
#include <sstream>
#include <list>

using namespace std;

list<int> split(string str) {
    getline(cin, str);
    istringstream s(str);
    list<int> numbers;
    int n;

    while (s >> n) {
        numbers.push_back(n);
    }

    return numbers;
}

int main() {
    string line, wagon, listMergeVagons;

    list<int> trackA = split(line);
    list<int> trackB = split(line);
    list<int> vagonsMerge;

    while (trackA.size() + trackB.size() != 0) {
        wagon = trackA.empty() ? "B" :
                trackB.empty() ? "A" :
                (trackA.back() < trackB.back() ? "A" : "B");

        vagonsMerge.push_front(wagon == "A" ? trackA.back() : trackB.back());
        wagon == "A" ? trackA.pop_back() : trackB.pop_back();
        listMergeVagons += wagon;
    }

    cout << listMergeVagons << endl;

    for (auto& w : vagonsMerge) {
        cout << w << ' ';
    }

    return 0;
}